Without knowing the reason why those users were banned it doesn't point to a widespread loss of accounts yet and if they were involved in activities not accepted on the platform, it would make the action to ban them justified.
Playgram as already mentioned has a process to identify accounts which belonged to someone even if they have lost access to it already, so the funds are not lost. A web version is also in the works.
Bans usually don't come without reasons and if it is not banned by automatic bots, it won't be likely mistaken ban and there are valid reasons for these bans.
If a banned user thinks it's unreasonable and unfair ban, ban appeal can be made. All platforms have their own rules and procedure for handling ban appeals but it only helps if the banned user is actually victim of some mistakes in moderation. If it is not a case, ban appeal will not help and lead to any ban uplift.