PupsiMax Edit 2: Just double checked one of the accounts they sent in the email, Nitsta, every season/cup they played in was before anything on the Krow account. Why is it being brought up now? How could it have been used for sandbagging if it was never used at the same time as the Krow account?
I would be more sympathetic but some parts are not adding up. You didn't actually say whether these alts are yours (or your roommates) or not, so are they? Why this many accounts? Especially since they are also both younger than your "mains". You also omitted the fact that one of the alts did in-fact play during 2020. So that means that sandbagging was actually involved. Not to mention, if the account that played before krow started, that means that the admins were not able to make a truly informed decision about what divs she should've been allowed to play or be restricted in.
Plenty of people in RGL have roommates, old forgotten inactive accounts, or old RGL accounts and I've never seen someone get banned for that; it just gets marked as an old account. You seem to be moving the goalpost by saying that "oh they're old though!". Just because you two are separate people does not mean you were incapable of any wrongdoing.
Why ban the alts only now?
I don't know but maybe it was not considered to be necessary. As you said; they have been inactive. Possibly, they are not the only ones. You are equally able to lie or omit information as RGL is.