Shem wasn't a banker or any other kind of criminal.
Apparently even Charlie disagrees with you, since he is pleading guilty.
That doesn't mean that he is actually guilty. He was given an impossible choice, if he pleaded not guilty he faced up to 30 years in prison, by pleading guilty he only faces up to 60 months. Nobody would risk that even if they were completely innocent, doing a couple of months is clearly a better choice than risking getting up to 30 years, you can't predict what a judge/jury will do. The fact that they offered him such a deal speaks volumes about how strong their case was.
94% of people in the US plead guilty to their charges as part of a plea bargain, in both federal and state cases, source:
https://www.bja.gov/Publications/PleaBargainingResearchSummary.pdfPlea deals just show you that the government prosecutors and politicians don't really care about the crime or the punishment. They're just functionaries that are only interested in their conviction rate.
This guy is making a name for himself at Charlie's expense.