After the hellban several years ago all his submissions were automatically killed instantly after posting. So you can't blame the community for not responding, the system made it impossible to respond/upvote at all.
This is one of the reasons why hellbanning is such a bad idea, leaving the poster to believe that everybody is actively ignoring him instead of just not being able to see him/interact with him.
Making regular healthy people waste a lot of their time posting content and feeling totally ignored is bad enough, subjecting people with mental health issues to that is even more unethical.