Most of those are crypto scams. The IG account starts posting about how they got rich on crypto. This is a very prevalent scam.
Clearly they do this to get a decent follower count initially for their spam bots, but my word is anyone who follows John Doe actually going to believe a scam video that is clearly not John Doe coming from John Doe's account claiming to be him? There has to be more effective angles.
It might be instead that your friends re-used a password that was leaked/stolen from somewhere else; anyone with a non-trivial number of online accounts using the same email will be listed in multiple leaks on aggregators like https://haveibeenpwned.com/.