Basically, as I understand it, the large social media can choose to abstain from censoring and enjoy being exempt from liability, or censor and leave themselves open to being considered to be "publishers" and thus leaving themselves vulnerable to being sued as a consequence for any questionable content they allow to be published (or just miss).

For the life of me I cannot understand why anyone of them would choose the later. 🤔

The NYT published a fairly good run down here.

Edit: congrats on another top trending post!