Good luck finding every single penny of money that person defrauded to take back, also good luck on preventing that outside of jail he don't use his network to still benefit old acquaintances and indirectly receive enough "help" that he lives a comfortable life outside of jail even doing "community work".
There isn't many things more violent than robbing trillion dollars from taxpayers and through very inneficient healthcare, security and others see thousand people die. That is much more violent than shooting someone.
Do you really believe that someone who's just been sentenced for financial crimes and lost all of his possessions will just go out and do major crimes again? Do you believe his associates will still associate with someone who's monitored? If you believe that a person cannot stop doing crimes even after they've been sentenced you might as well just kill them. No amount of prison time will change that person.
The problems you are describing are rooted in the system and not single individuals. Capturing them and throwing them in jail won't help anyone and be nothing more than a drag on society. Kill them or set them free, prison is a no-win game.
Not sure where you are getting your law information from.
But exactly because people that are facing severe law enforcement usually keeps their ties (after all they are mostly unknown to the prosecutor) and several of them try to jeopardize investigation or trial that we do have preventive jail time to cut the ties of that person with his associates.
You are assuming he lost all his possessions. He at most lost the possessions the prosecution could find, very possibly most of the money is still located in places prosecution have no idea about.
Also if that person have a lot of network he also have chance knowledge and could talk about the other people to have a smaller conviction. So those people could keep giving him some money for him to keep shut.
I would be fine with killing them. But Brazil doesn't allow capital punishment. Well even USA don't allow for corruption, on this China is better off than us.