You hit the nail in the head, Calli. He's a scapegoat and a moneymaker all at once.
It's such a messy situation with so many different perspectives. It also feels incredibly haphazard, considering just one month ago he was announced to return to the group. Seunghan now has about another year to hustle and get his concept in order, as well as his mental health in check before he has to face the masses again.
Overall, it's a nasty move on SM's part. Re-debuting means admitting that Seunghan is a good idol and an asset to their company. He's good enough to go solo at only 21. If he really is that excellent, then he should've just stayed in RIIZE and had the company properly deal with the bullies, the funeral wreaths, the online harassment, et cetera.
Like you said, I really hope he's doing alright. And hopefully, he still has the support of his members. He'll need their love and encouragement to go into this next phase.
And lastly, I hope every bully and OT6'er has a horrible life. Fuck all of them for ruining a young man's life over something as simple as a girlfriend and a cigarette.