She wasn't so vocal previously; maybe she was the same kind of person back then too, but it wasn't evident since people were judging her solely based on her work.
Oh I've no doubt that she's always harbored these views. More that if she'd just kept her mouth shut, she'd still be mostly adored. Like there'd still be some people looking at her with a critical lens, but most wouldn't care.
People will probably study this phenomenon for a long time to come, but people become wildly fanatical when a person in power shares their bigoted views and people in power can't seem to resist turning it up to 11 because those types of fans make you feel like an absolute god.
Maybe from her POV being famous for writing the books became mundane, but all these people suddenly treating her like she's a sociopolitical genius probably hits that reward button so well she just can't stop taking another hit.