Because our world is imperfect and justice not always finds the guilty. In this case, his karma finally caught up with him. He was guilty, he behaved like an ass and he got 3.5 years, even though if he didn't he probably would get much less. I can see EFFs point that 3.5 years is too much too, though I personally feel very little sympathy to Auernheimer. If he wises up, he'd be out in less than 2 years probably, if he doesn't, well...