Man did so many wrong things, helped terrorists to launder millions of dollars and this is the punishment for him? If you live in the USA and declare slightly wrong income, you might face prison.
Do tell me, how many years in prison did Deutsche Bank CEO got for laundering
10 billion dollars? Or they just paid the fine and went on with business as usual.

Why? Because of corruption? By the way this looks like a corruption, the difference is that stakes in the US are one of the highest.
Because people as rich as CZ rarely go to prison for stuff like this in vast majority of countries. As a matter of fact, I read somewhere that he is the richest man ever that will end up in prison serving time.