That's not true though. Social network sites existed, just not so "centralized" and "viral". Facebook created a simple and more user-friendly interface. WhatsApp as it understand, does not make much if any money. Instagram is a cash cow due.

They have released some good open source technology, but as the OP said, Meta hasn't much going for it apart from addictive apps for showing ads

They also had the right audience to build the early adopters: top university students.