The reliance on the three didn’t become a thing until Steph came around. Some people emulated him, others realized that statistically you have a better shot of winning by shooting a lot more threes.
I could be wrong, but I’ve seen similar takes from other people as well.
It started slightly before that. I remember Chris Bosh saying that when Shane Battier was on the Heat with him he's the one who convinced him to just take a couple steps back and start taking more 3s instead of long 2s. Steph made it explode, but that 3 point increase was already in the works before that 2015 Warriors team broke the damn open.