Anything else is "doing something he likes while avoiding the consequences for all the illegal actions he did in the past", and we're not talking about somebody in poverty stealing food at the supermarket, here.
(This is all assuming he's guilty, of course this has to be demonstrated at the trial)
If he were going to continue living a quiet life there til he died, I have to wonder what we've actually gained here. Yes, he did awful things. I'm not denying that, but nothing we do to him is going to change that. I'm not really convinced that cracking down is going to prevent future crime; it doesn't seem to have stopped the mafia thus far. He's not going to talk, the investigators have called out that they can't make inroads because of their brutal code of silence.
The only thing we get out of this is a sadistic pleasure from punishing a man who seems to have reformed. It's justice porn. Why would anyone on the run from a life sentence bother to try to reform then? You may as well stay in the Mafia; there's nothing for you on the outside.
However, because we want people to come clean of their own agency (both to make crime-solving take up less public resources, and to make it such that criminals don't have to wait to get caught before becoming productive and non-harmful members of society), we should adjust incentives such that the punishment for coming clean of one's own accord is a little less, and the punishment for getting caught for the same crime is a little more.
Maybe it could be implemented as adding an extra punishment for concealing a crime?
For all we know he could have been operating a human-smuggling operation from his current local.
Either way he knowingly and purposefully avoided prosecution.