This has been a very gradual change. The earliest announcement I can find is from 2018[1] but I'm pretty sure it was in the works long before. That's more than five years to implement a technology that browsers and servers at the time already had known how to do for a decade or more.
I don't think changes are hard to push forward. Soon every website will require SSL. Tech giants can move the needle on adoption of new standards.
Wanting to stay in contact with your customer is a pretty big forcing function for adoption.