It is the duty of columnists to explain things. And, among the columnists, those most esteemed are those who tackle the really tough questions. This, dear reader, is one of the days that a columnist earns his pay, because the issue before the country is: why was the World Series so late arriving this year?

More has been said about the fact that this year's Series had the latest starting date ever than about the skills of Fernando and the Goose, the ageless Nettles and the nettlesome Steinbrenner.

But all this prattle about the overlap with the eighth week of the National Football League and the third week of the National Hockey League is beside the point.

Everyone knows the Series was delayed, first by the mid-season strike and then by the owners' desire to recoup a bit of second-season drama (and revenues) by inserting an extra round of playoff competition between the first- and second-season division winners.

What no one seems to acknowledge, in the carping at the great men who own baseball, is that they were merely carrying out two of President Reagan's basic policies.

The owners were union-bashing, giving their overpaid minions the same cold-water treatment Reagan gave the air traffic controllers. And they were cashing in, just as the corporations did, on the Reagan tax cut.

The people who complain about the lack of a "real" baseball season are probably the same soreheads who get semiviolent just because they sit for three hours at LaGuardia, waiting for one of the remaining controllers to clear their shuttle flight for the 36-minute hop to Washington.

Stranded travelers should recognize that these forced delays are really opportunities created by President Reagan for getting to know your neighbors on the plane.

In the same way, the mid-season baseball strike was created by Bowie Kuhn to allow husbands to spend their summer weekends at family picnics and outings, instead of being glued to their television screens while their wives and children frolicked without them.

But targeted compassion is one of the main themes of the Reagan era, and there are some fans who truly need baseball. The owners, understanding that, brought back a dose of baseball in the second season for the "truly needy."

The other major theme of Reaganism is worthy greed, and baseball epitomizes that as well. Look at the teams that were involved in the interminable playoffs. No poor boys there. It was a case of the rich getting richer--surely the Republican way. Now, two of the richest of them all, the Yankees and the Dodgers, have been filling their coffers as Halloween approaches.

Do not doubt that this cash collection by the wealthiest of the baseball conglomerates is socially useful. In true supply-side fashion, they will use the added revenues to hire away even more ballplayers from the less wealthy clubs in the next free-agent draft. Eventually--about the same time the housing and auto industries revive--this wave of prosperity will boost the take-home pay of the hot dog vendor in a Three-I League park in Terre Haute.

But I digress. The point I set out to make is that complaints about the baseball season being too long are all wrong. They are out-of-date thinking.

In the new age of Sun Belt government, the whole concept of "season" needs rethinking. What do Los Angeles or Houston know of seasons? I am reliably informed that our Sun King president had so far forgotten the autumns of his Illinois youth during his long years of residence in Southern California that when he saw the foliage changing at Camp David, he turned to Ed Meese and said, "What's that?" Meese, having lived in San Diego, did not know either, but a National Security Council staff study is expected to clear up the mystery soon.

Those who complain of the endless season are stamping themselves as unfit for the Reagan era. It is out-of-date thinking for a time when the rule is: adapt or perish. Big league teams unfortunate enough to be located in cities where there are seasons will have to acquire domed stadiums--or yield their franchises to the waiting groups in Phoenix, Tampa and Tucumcari.

Or, they may wish to join the extremely small, disgruntled band of Chicago Cubs fans who have a truly radical solution to all this. We favor a two-game season. That way--and only that way--we know we'd be in the pennant race on the last day of the year every year.