How did posting online change from, "Be careful what you put online!" to many sharing a lot under real names?

https://lemmy.world/post/1458177

Facebook. Simple as.
Definitely Facebook's policy of demanding real world names and crushing down on anonymity and pseudonyms, around 2014: https://www.protocol.com/policy/anonymity-real-names-jeff-kosseff#toggle-gdpr
How Facebook’s real-name policy changed social media forever

The debate over anonymity extends to every corner of the internet, but may matter most on social networks.

Protocol
EYY I remember when they did that. That’s when I quit cold Turkey
Yep, most definitely. They were the first.