A Libyan television editorialist, speaking against a background of modern tanks bucking across the desert, was denouncing President Reagan the other night as "a hateful crusader" when, without warning, film clips of a 19th century cavalry charge flashed across the screen.

Unperturbed, the speaker went on exhorting his listerners to defend Libya as the "base of a new Islamic civilization," until he was cut off in mid-sentence by a muezzin calling the faithful to evening prayer and the backdrop faded into a shot of a mosque surrounded by spring flowers. As guests at a seaside hotel here heard the plaintive Koranic verses, they noticed the aggressive musical beat of "Saturday Night Fever" intruding on the holy chants.

"God help us," sighed a Lebanese businessman, rolling his eyes.

Life in Libya these days is an exercise in such stark and sometimes zany contrasts. For the businessman, it is a country with vast oil revenues to spend but with a bureaucracy so untrained and jumbled that he cannot find the right official to deal with.

For 1,500 American residents now on their way home, it is a nation with people of warm hospitality despite relentless propaganda depicting Uncle Sam as a blood-soaked grim reaper or, according to a poster glued to walls all around Tripoli, "the leader of world terrorism."

And for diplomats trying to analyze the leadership of Col. Muammar Qaddafi, it is a puzzling regime that in theory has abandoned government in favor of "direct popular rule" by "people's committees" but in fact holds real power closely within the five-man Revolutionary Committee of Army officers who brought Qaddafi to power in 1969.

Somewhere in these contrasts, the diplomats say, lies an answer to the question of whether the Reagan administration is right in charging that Libya has dispatched hit teams to assassinate the U.S. president or other high officials. Although none of them professes certainty, the European analysts here generally consider the accusations overdrawn because of what they say is a new effort by Qaddafi in recent months to shed his image as an international troublemaker.

"Unless the Americans show us some proof, we cannot support them," said the ambassador here from a West European country known for friendly relations with the United States. "And they have shown us nothing."

The Europeans have direct experience in the subject. A dozen Libyans voicing opposition to Qaddafi's rule have been shot in Britain, Italy, Greece and West Germany during the last 18 months. In most cases, investigations indicated Libyan gunmen pulled the trigger on orders from someone in Tripoli. As for France, its embassy here was burned in February 1980, two months after the U.S. Embassy was sacked.

Responding to official protests, Maj. Abdulsalam Jalloud recently told the Europeans the terrorism sprang from overzealous "Revolutionary Committees" whose youthful members got out in front of their leadership. Jalloud, Libya's second-most-visible leader, assured European envoys that such violence would no longer be tolerated.

Jalloud's assurances were welcomed and to some extent believed. But his explanation -- a sort of revolutionary "boys will be boys" -- inspired skeptical smiles from diplomats experienced in dealing with people's rule as practiced by Qaddafi's government.

Libya in principle no longer has a government. Indeed, it is no longer a republic, but a jamihiriyah, an Arabic neologism meaning roughly rule of the masses.

Ministries have become "secretariats," managed in theory by a "popular committee" composed of bureaucrats and other interested citizens who may or may not have practical knowledge of what the secretariat is supposed to do. As a result, high ministry officials spend a lot of time dealing with personnel questions raised by the committee and explaining what the secretary--who used to be called a minister--is trying to accomplish.

In fact, however, separate Revolutionary Committees parallel the people's committees in ministries, towns and villages. The Revolutionary Committees are officially assigned to inspire and animate people's committee members. According to well-informed foreigners whose observations are borne out in private conversations with Libyans, the Revolutionary Committees actually are there to make sure Qaddafi's prior decisions are approved.

It is against the background of this steering system--staffed largely by young zealots--that European envoys here dismiss Jalloud's suggestion that terror teams could have left without approval from the top.

"We know that in 99 percent of the cases, the Revolutionary Committees are kept in a straitjacket, that they are told what to do," said one diplomat. "So why would they be able to do something like that on their own? "

In practice, he added, Qaddafi personally shapes all major decisions on oil policies as well as foreign or military questions.

The 39-year-old revolutionary chief has just one title, commander-in-chief of the armed forces. He is referred to in official Libyan parlance only as "brother leader." In addition, he is reported to take special care to include the top Revolutionary Committee's other four members in what are presented as collective decisions. But foreign analysts here say that behind the scenes he increasingly has taken personal command in recent years, with only Gen. Mustafa Kharoubi, chief of staff and head of military intelligence, able to discuss his orders.

Qaddafi is the Army's undisputed commander, with Yunis Abu Bakr, another member of the top Revolutionary Committee, relegated to a role as day-to-day "military executive." In crisis situations, such as the recent Chad intervention, Jalloud assumes his rank as number two. It was he, for example, who traveled to Ndjamena after President Oueddei Goukouni asked the Libyans to leave Chad.

Well-informed European diplomats here believe Qaddafi's Soviet military advisers are well placed to exercise considerable influence. For example, high-level Soviet officers work in the general command headquarters next door to Qaddafi's own offices in the Bab al Ziziah compound. In addition--and perhaps more important in the long run--an estimated 3,000 Soviet advisers or their Eastern European colleagues are present wherever modern Soviet-made weapons are used in the Libyan armed forces, the sources said.

That means at almost every level. But the diplomats caution that it is impossible to tell how much Qaddafi listens to their advice on any given issue or how explicitly the Soviets can control use of the sophisticated weapons, including Mig25 warplanes, that they have sold to Qaddafi. Some analysts conclude from the Gulf of Sidra confrontation in August, in which Qaddafi lost two SU22s, that Soviet control is loose at best.

Western intelligence reports say East German experts also help run Qaddafi's internal security apparatus. However, European diplomats on the watch for the East Germans say they are never seen. In contrast, Soviets and other East Europeans regularly prowl Tripoli streets on Friday afternoons off.

Qaddafi's movements, although erratic in what may be a deliberate attempt to avoid setting a pattern, do not appear to reflect fear of hostility from his people, diplomats here say. In their judgment, apart from a merchant class deprived of its property and earning power, Qaddafi's standing in the Libya public remains high.

Following a tradition set soon after he took over in 1969, Qaddafi occasionally shows up unexpectedly at the wheel of his own car to preside at factory dedications or similar ceremonies. When he does, visible security is light.

But at least one attempted military coup has been reliably reported against Qaddafi, demonstrating that some officers oppose his rule. With the military largely closed off from the rest of society--and completely out of view for foreigners--it is difficult to assess the extent of dissatisfaction among the increasingly educated officer corps. Qaddafi is uncertain enough to have his headquarters compound guarded by a pair of T62 tanks installed in concrete revetments and to work deep inside an inner office whose access is a narrow, reinforced door.