I think Zuckerberg's conduct and various flip-flops in past few years mainly have to do with the massive backlash he received for his alleged role in 2016 election. Someone had to be a scapegoat, and Zuckerberg served this purpose perfectly, by allegedly allowing Russians to manipulate or steal election from Hillary. Zuckerberg's cause wasn't helped by his early moves in 2017, when he went on high publicised trip to Iowa to explore possibility of being Trump after Trump, something the entire US establishment apparently wasn't prepared to.
And, after myriad of documentaries accusing Facebook of being spreader of fake news and manipulation and Zuckerberg himself being dragged to the mud at Congressional hearings, he apparently got the message and decided that he would be a good boy. Hence hundreds of millions of donations for Biden and censorship.
Of course, once Elon made his play and helped Trump get elected, Zuckerberg is suddenly changing the tune.