My own view of why the academic world is so to the left is because everyone uses whatever levers they have to gain their own small allotment of political power. Insinuating oneself into the decision making hierarchy for someone at a university is to put together some perspective that will convince others to follow your own lead. Being anti-establishment is the only means for the young, and for those who never grow up.
Here, however, is a review of a book, Why Are Professors Liberal and Why Do Conservatives Care? that looks at the phenomenon through the eyes of a leftist academic. The reviewer’s own conclusion:
The key moment, Gross maintains, is the decision whether or not to go to graduate school. Young conservatives may not know all that much about academia at the faculty level, but popular stereotypes and a few off-putting experiences in class can sufficiently discourage them from pursuing academia as a site for success. A freshman orientation session that divides white males from everyone else, incessant talk about diversity, multiculturalist reading assignments, and so on may not bother them that much (and they can always find safe spaces such as College Republicans), but such things do convince young conservatives that staying on campus as a career move is foolish. An English major who reveres Great Books needs only one occasion of a teaching assistant ridiculing him for a dead-white-male fixation to decide, ‘I don’t need this.’
For a conservative, it’s pretty bleak in the academic world, but then it’s pretty bleak just about everywhere else as well.