Every judge in the US had exactly $4.3 billion reason to sentence him as little as possible, because it's no secret that money and snitching make a winning combination, especially when it comes to the US judiciary. Considering how long CZ danced on the thin line between legality and illegality, all that he paid in money and a little time behind bars is a small price for what he should realistically get.
What needs to be admitted is that CZ is not one of those losers who don't know how to play the game, of course I mean people like Bankman or Do Kwon.