The word "TERF" to describe the people and worldview that wanted to exclude trans people and trans rights from social justice activism wasn't even recorded as existing until 15 years ago, not because those views didn't exist - they're traceable in basically their modern form all the way back to like the seventies and are oddly pervasive - but because they succeeded well enough that even discussing the idea that this was a bad thing didn't start to become a part of activist discussion until then. This whole shift in viewpoint to that becoming unacceptable is incredibly recent.
Also, in general ordinary non-terminally-online people were much, much less anti-trans than both the "attack helecopter" anti-SJW side and the anti-trans campaigners that social justice activists were meant to sympathise with, though that may not have been obvious since one of the big things that was unacceptable was actually talking about what anti-trans people on the same side were doing and the real-world consequences (including stuff like laws they lobbied for). Admittedly, I'm from the UK so my experiences may not be representative of the US and other countries, but we are supposedly "TERF island" so that cuts both ways.