9 years may be excessive, but if it sets an example others might be less anxious to start their own little spam enterprises.
Giving him a few weeks of community service wouldn't have caused more than a byline in a local newspaper (if that), giving him 9 years makes sure the case gets worldwide attention which may well have been why the verdict was as it came out.
So he's a sacrificial black goat. So what? He's out of the running for a good while.
While he wasn't responsible for all or maybe even most spam, he was responsible for enough to get law enforcement interested...
Take down the large ones and the small ones will fall by the wayside. The small ones are the ones easiest to block anyway as they're not the smart ones (if they were they'd be large ones).