He can be tried and sentenced in absentia. (The problem is, as long as the profit is so insanely high, and the risk is relatively low, thousans will try to take his place.)
I think it is the pictures of a former king pin being tried sitting in a court that prosecutors want, it sends a message that no one is above the law. Being tried in absentia doesn't really tick that box.
Representative democracy can be done right. An independent Anticorruption Agency with investigatory and prosecutory powers irrevocably granted by the constitution, but with narrow scope, can work wonders.
Of course, above a critical mass of amassed power/popularity, nothing can stop a dictator to simply do re-found the state with a new constitution, but at that point it's very much a coup anyway.