I think part of it is realizing that there are a lot of benefits that come from giving lower priority to cars. You increase density, you can now live in a neighborhood where you can walk to do all your errands, you feel more safe when your kids are outside or crossing the street, you feel more safe biking around and getting exercise at the same time, etc. It comes with a larger movement of urbanism.

Can't say why the movement picked up exactly, just like everything, there are cycles, and after decades of building highways all over our cities and realizing how bad the situation got and how it never really "solved" traffic, there's just a return to a different way of planning cities.