This is a known problem and (probably) there are systems which should monitor automated abuse of abuse.
However, all those social networks (including Instagram) are susceptible to another attack - just rent a horde of low-grade bots... and add the victim's account to their friends. This sudden increase in friends count are treated as an attempt to boost the rating of the bot accounts => ban not only for the bots (about whom you don't care) but for the victim too.
Perhaps OP is in the similar situation, though probably his spouse wasn't a target but a collateral.
I don't know about whatsapp but on tiktok you can easily do this successfully, without bots - they automatically permaban anyone who is reported just a handful of times.
All you have to do is make a few accounts or convince a few friends and you can remove any video or account on the app that you want.
Considering this thread, it looks like Whatsapp is the same way.
So if I get a bunch of bots I could file mass complaints about someone's what''s app account and det them banned?