So from what I've read, he had the option to plead guilty to some charges and I'm sure spend very little time in jail, but he didn't want to plead guilty at all. He had options.
So the two options were:
1) Plead not guilty, case drags on for years, costs $millions to defend, get convicted, serve 2-3 years in jail, unable to fight for something you believe in during that time
2) Plead guilty, case is over quickly, not expensive to defend, get convicted, serve 2-3 months in jail, get on with fighting for something you believe in