She had been on conspiracy rants long before she was fired and even before the show was revived, and it took her calling a black woman a monkey for any sort of blowback on the actual show.
https://time.com/5294402/roseanne-cancelled-abc-racist-conspiracy-theory/
And no, it didn't start with Trump. It's only recently people have been facing even a general sense of consequences for their behavior, but criticism of people making sexist, homophobic, and racist statements or actions is not by any means a new thing.