As for someone that's been "anti-car" for quite some time, I'm not sure why it's suddenly exploded. But I think lots of people enjoyed the cities more with less traffic during covid, and realized the streets can be made for the people, not metal boxes on wheels.
One other factor is global increase in house/rental prices. Seeing your local government prioritize parking instead of housing, or NIMBYs blocking new development, has angered lots of people and they're now taking action. Or cities spending billions on adding yet another lane to their 26 lane wide highway while the public transportation is famished.
Also, with people feeling the rising cost of living etc, it's easy for people to look for ways to remove what is a huge chunk of their spending: their car.
Additionally, lots of great contents the later years. Strongtowns, NotJustBikes etc is orange pilling lots of people that have already started to be curious about these issue. Driven by memes from fuckcars etc, it's become a movement.