Particulars are irrelevant. You paid years ago for a game and Steam will ban your whole account because of another game.
Even relatively simple games tightly integrated with Steam are basically rendered non-functional after getting in the poor graces of the facilitating platform. At that point, your only hope is to learn the way of the Linker, and brush up on Reverse Engineering skills and you might be able to get something working after excising or replacing the library call implementations of the people who banned you.
The other thing is that there is no source cited at all, and no ban type specified at all. To me, banning means that a user can no longer log in. But Steam actually applies a wide range of restrictions to an account: https://help.steampowered.com/en/faqs/view/4F62-35F9-F395-5C...
The "20.000 ban" issue is further discussed on Reddit, where it's labeled as "misleading".
https://www.reddit.com/r/Helldivers/comments/1d43qql/helldiv...
Also, I'd like to emphasize my original argument. The risk itself comes from trusting a service, and furthermore, from consciously violating the terms of service. And using VPNs to make Steam behave different is against the terms of service. Information can be found here, when searching for "proxy":
Or perhaps it's just my impression because I don't touch the competitive multiplayer stuff.