He made a bunch of mindless comedies back in the 80s-90’s that were moderately entertaining.
Rob Reiner directed The Sure Thing. Maybe he got in Cusacks head. It happened to Tom Cruise. He was apolitical at worst, was proud to make Top Gun, and then he worked with Paul Newman. Newman educated him about how terrible it was to make a jingoistic, pro-military movie, and next thing you know, he was spouting liberal crap and making an Oliver Stone film.