He was general counsel for Verizon, which is typical for regulatory capture stooges as far as career choices go, but worked for Jenner & Block, who's primary public record is heavily left-leaning. He's an Obama appointee, but on the recommendation of McConnell.
My guess is that Jenner & Block probably fronts a lot of left-leaning legal cases outside of their bread & butter, which is telco, giving them a good face across the board with Congress. Meanwhile, his prior appointment to the FCC was almost certainly a horse trade between McConnell and Obama.
Pai has been more or less a telco puppet for the last 15 years in one role or another.
The interesting thing about this is that regulatory capture is generally in support of further regulation rather than against. This implies that net neutrality is actually either a grass-roots regulation (highly unlikely), or there is an inversion of concern over the general case. My guess is that the monopoly positions that telcos hold has inverted the normal regulatory capture process at the FCC, and that the primary consumers of the content (Amazon, Netflix, etc) are very shrewd operators who can see through regulatory rhetoric.