Oh I don't do that for that, there's multiple reasons, but one of the bigger ones is to promote smaller instances because of the volume of posting it makes smaller instances more recognizable.
Other reasons for the multitude of accounts include making comms on fitting smaller instances (I make programming related comms on programming.dev or retro related on retrolemmy for example), protecting against the imposter problem and better interconnecting wayward smaller instances (you'd be surprised at the number of, even common comms, that smaller instances are missing out on that I discover just through my posting)
I specified already, people see the instances you post from and builds recognition for that due to the volume with which i post. So I rotate around which ones I post from
I haven't posted to a .world comm (with the exception of linux_gaming) since the JL fallout and have moved quite a few of the comms I created there off it and am planning to move some of the larger ones I mod off there
It actually did happen to me, and they were spouting right-winger Nazi bullshit sooo yea. Turned out it was UM (unsurprisingly) lmao
And btw some of those accounts in your screenshot are the imposter accounts like Lonestar, az.social and pawn
But some of the others I don't post from much if at all and just make comms with them