Consider a political view that is out of fashion--conservatism or libertarianism c. 1960, say. Not many academics, not many authors, support it. But the ones who do are committed supporters because nobody else would pay the costs of being on the outside. And, on average, they will be abler than the opposition, both because they have been exposed to both sides, the other being all around them, and because surviving intellectually when everyone thinks you are wrong is hard work.
Suppose some change, say the Reagan revolution, reverses the roles. One of the reasons for the change is that the outs, while less numerous than the ins, were of higher quality—more committed, with better arguments. It is hard, after all, to do a good job of rebutting views that you don't take seriously and, in any case, are rarely exposed to.
Now being a conservative is not only respectable, it is the route to a good job in Washington, perhaps a profitable and prominent career. The number who choose to support that position increases sharply but their quality decreases, both because it is much easier to maintain a position when it is in favor and because quite a lot of them are rice Christians--the equivalent, in the intellectual and political world, of Chinese who converted to Christianity because the missionaries had rice.
On the other side, things are moving in the opposite direction. Only those who really believe in liberalism (modern American sense) continue to support it, now that it looks more like the wave of the past than the wave of the future.
And since the new ins are getting flabby, and the new outs, if less numerous, are now of higher quality than they used to be, the wheel turns again.
Not, I am sure, a full explanation of political cycles, but perhaps at least a partial explanation.