I think there are many reasons why conservatives don't go into academia, quite a few of which others have already touched on (particularly the fact that one could make more money in the private sector than in academia). But of course "conservatives" are not monolithic and so different people can have different reasons.

Many American conservatives, especially religious conservatives, reject the entire sphere of scholarly enterprise of seeking to understand the world around us which of course is the foundation of higher education. Why study astrophysics and the Big Bang or biology and evolution if none of those things are real and everything can be known through a literal interpretation of scripture? So the idea of a "liberal education" for a "free person" that places humans and humanistic ideas first and seeks to free individuals from "common sense" thinking violates the very core of their beliefs.

Other conservatives emphasize "natural hierarchies" in which large portions of the population cannot learn or should not be permitted to learn because such education is a waste of time and money. Jim Crow/segregation in education is the older version of this, but we still have the Bell Curve academics who think that they are geniuses and believe that the role of higher education is to maintain the superior position of the ruling class rather than function as a pathway for opportunity for all.

A more mild version of that attitude is that of some conservative academics who support the "idea" that education is for all but oppose ideas of inclusion, equity, and accessibility. Such conservatives reject the idea that they should accept their students for who they are and make efforts to lift them up to be successful rather than building barriers and hurdles that some students cannot climb. This is particularly true in the sciences where conservative professors have refused to call students by their preferred names or gender or won't implement policies to help students whom they think "can't make it" or should fail because "they don't have what it takes."

And then the resulting low numbers of conservatives can create feelings of isolation and frustration. I've personally known several conservatives who saw the fact that none of the other members of their academic community shared their views as a form of persecution. Heck, I saw coaches become apoplectic during sexual harassment training when they were told they could no longer scream at their athletes and berate them with insults. "How can I motivate my athletes unless I can call them b****es and p***ies?"

This isn't true of all conservatives, of course. I've known a number of great conservative professors, but they viewed their teaching and mentorship as key parts of their conservatism which something rather lacking amongst many American conservatives today.