Can confirm. Before FB, almost nobody told their real name online. Nowadays you can easily find out who is a racist and who believes in conspiracy theories just by looking at what they post. Usually there’s also their real name and face attached to the post so that you can be sure who you are talking about.
How did this happen? FB made it normal and almost obligatory.
Why did it happen? So that FB could make more money. Simple monkey brain people like to socialize and share stuff with everyone, and FB is simply exploiting that vulnerability.