VAC has never banned any account for "nothing" or "no reason" unless those are the names of the cheats that were detected.

1 VAC ban on record | Info
407 day(s) since last ban

VAC bans are permanent, non-negotiable, and cannot be removed by Steam Support....and also cannot be removed by anyone on this forum.

VAC bans are delayed from the time of the detection to the time that the ban is actually applied. What you were doing when the ban was applied, is irrelevant.

https://support.steampowered.com/kb_article.php?ref=4044-qdhj-5691

all VAC bans come from the detection of a known cheat, whether it is used on the account itself or some sort of sharing has occurred (account, library, or phone number).

Users are responsible for the security of the account and all activity on the account.

407 days later, your VAC ban is still permanent.
If the ban would have been a mistake, it would have been removed a year ago.

Keep in mind that Rainbow Six Siege does not use VAC.

That's because VAC bans are permanent.