THE OTHER DAY, in case you didn't notice, Diego Asencio arrived back in town. He had been in Bogota for some time, held captive, actually, in the Dominican Embassy there until he and some others were exchanged for something like $2.5 million and a safe conduct pass to the merry isle of Cuba. This raises two questions: What do you do with $2.5 million in Cuba and how come the Marines were not sent in for Asencio?

The answer to the first is beyond me -- and somewhat beside the point. What is more interesting is the second question because it tends to highlight how the Carter administration turned the Iranian crisis into something else --- a-do-or-die, hold-your-breath kind of super-crisis.

It is hard to know exactly what to call the Iranian situation since the word crisis is so overused. Suffice it to say, though, that this was not the first time Americans had been held hostage and not the first time the American government had to deal with a hostage situation. Exact parallels are hard to find, but the Pueblo, an alleged spy ship, does come to mind. It was seized off the coast of North Korea in 1968 and its 88-man crew was held prisoner for the next 11 months. One crew member was killed when the ship was boarded by the Koreans.

It is true, of course, that the Pueblo was spying (outside Korean waters, we maintained) and it is true that the men who were seized were mostly military and it is true that, strictly speaking, the North Koreans might have deserved the apology they demanded and later received. (It was immediately repudiated after the crew was safe and sound.)

But it is also true that in the minds of the Iranians, our hospitality for the former shah was an outrageous act made all the more outrageous because we were the government that helped topple a constitutional government, returned the shah to power and kept him there. What they want, too, is an apology.

It is hard, of course, to compare national indignities -- to say whether the capture of the Pueblo was worse than the capture of the hostages in Iran. It was just different. But what can be compared is the way the Johnson administration reacted to the Pueblo affair and the way the Carter administration has reacted to the Iranian one. Carter has totally blown his cool.

Faced with the prospect of dealing with a bunch of crazies, radicals, zealots and outright fools, Carter chose to do just that -- deal with them. He treated them as if they were a real government. He talked to them. He negotiated with them. He threatened them. He bluffed them and finally he tried the commando raid. He gave them all the attention and limelight they could have wanted. You have to suspect that if the militants had not had Carter, they would have had to invent him.

Johnson, on the other hand, did no such thing. He did not announce that he was going to stay in the White House until the crew of the Puelbo was freed and, in fact, he did not. He did not announce in some fashion that henceforth the Puelbo would be issue number one and that nothing -- not anything -- would be normal until the crew was freed.

Carter did precisely this. He turned Iran from a crisis int something else. He made it numero uno on the agenda -- the single, dominant issue of the presidential campaign. Remember malaise? Remember Afghanistan, for a brief, glittering moment the greatest crisis since World War II? Remember the economy? The moral equivalent of war? All that faded. Only Iran stayed on center stage, helped by Carter's refusal --until yesterday -- to compaigen.

To an extent, us guys in the news media played into the president's hands. We cleared the deck for him. ABC launched its series of mini-specials, vowing in almost Carterewque terms to continue the programming until the hostages were freed. The network called its show "America Held Hostage," which is catchy, but a wild exaggeration that does manage to wave the bloody shirt just a bit. CBS was so rattled by this competition that, it on one occasion responded with a special about the eviction of newsmen from Tehran -- an event so momentous you probably already forgot it. No matter -- the newsmen have returned.

But presidents control the news. They set the agenda and this is one that Carter himself set. For political as well as personal reasons, he made Iran his Alamo or his Maginot Line -- this far and no further. The question is why? The taking of hostages by Iran changed very little in the Middle East. It was far short of something as crucial to the world as, say, an Iranian closing of the Strait of Hormuz or the shutting down of all that country's oil production.

The taking of hostages is an outrageous act -- an insult to this government and its people, not to mention a human tragedy fo those involved. But it is not and never has been the most important thing going on in the world -- the linchpin of our foreign policy.

The happy presence in town Ambassador Asencio proves that these things come to an end, often, as T.S. Eliot once wrote, not with a bang, but with a whimper. This is the way it ended with Asencio and the Pueblo and hopefully this is what will happen with Iran. Maybe the way to speed the process is to do what the militants least want: ignore them. And then get back to business.