I'm pretty sure we're talking about "violence" in the abstract/legal context here. Or at least, that's how I think about it. I would say that stealing from someone is "violent".
There is no need to put such people in prison. How is that productive for society?
These people are clearly intelligent, so put them to work. Dock their pay until they pay off the damage they caused plus penalties to discourage future behavior.
These people are all motivated financially, so hit them where it hurts, the wallet.
what if they refuse to work? Do they just get to walk away?
Not saying the solution is prison but a lot of people who commit things like large-scale fraud are usually psychopaths to some degree, and might also not make the most "rational" decisions. Expecting "normal" reactions to such propositions might be a bit much.
> what if they refuse to work? Do they just get to walk away?
Nope. Then you can send them to prison. But at least give them a choice.
> people who commit things like large-scale fraud are usually psychopaths to some degree
Large scale fraud is rare. You want to send those people to prison, fine, but it'll be in the hundreds on an annual basis.
Small scale fraud is common. The motivation here is purely financial. They will want to keep out of jail and pay you money. It makes no sense to spend money to keep these people unproductive in prison. In fact, it's just outright crazy.
That's a non-violent crime, but it's still deeply disturbing for the victim.