Hi there,
Bans are meant to give the individual some time to process what happened and learn from their mistake. They are also a tool to restrict hackers and people who intentionally violate the rules from destroying other people's experiences.
As with most multiplayer games, we ban the person and not the account. Previously, we actually issued a permanent ban for anyone trying to evade their ban by using another Steam account. Nowadays, we have an automated system that simply does not allow them to play on other Steam/TruckersMP accounts as long as their main account is banned.
It is best that your friend waits until their ban has expired. As always, if they believe the ban is invalid, they can appeal it at https://truckersmp.com/appeals
I hope this helps