4 months because he cooperated fully with the authorities and paid billions in settlement, i don't think anyone who was interested and followed this case closely would be surprised by the sentencing, maybe he could have got a few months in addition, but that is that.
Who could be next in the list of crypto service owners to be arrested and prosecuted?
The rich is always the rich. The goal is to extort him and have it in history that he was prosecuted and imprisoned. He corporated with the law enforcement agents as reason to mitigate his punishment is valid, but surely others things happend behind the scene.
CZ is not only an international figure, he is also one of the faces of cryptocurrency. So, any judge dealing with him will have to be very careful, if not for anything, because of posterity.