He had a market, but simultaneously didn't if that makes any sense. The world didn't need another Twitter clone, it already had Parler and Gettr. Social networks are difficult to get users onto because people want to go where their "friends" are, so you're not just convincing one user individually. Getting wide enough adoption to where users actually use the platform regularly is difficult.
I think this is right. In addition, IMO ultimately it feels hollow if you can't piss anyone off. Twitter makes it possible to search for the living avatar of whatever you hate the most so you can tweet invective at them until your head explodes. It feels good, even for a moment, to tell your enemies what's what. If you're on a platform with only MAGA people, what's the point? I signed up out of curiosity after it launched and there was so little actual engagement. Maybe that's changed, I dunno, but at any rate, a key component of the MAGA movement was how much certain high profile people obviously hated it and felt threatened by it. (Whether one thinks they should have or not is immaterial to the fact that it thrived on the hate and contempt from mainstream liberal mores havers.) If you can't see them being mad at you for having your own social media network, it loses its charm.
Also, the fact that as far as I know Trump still hasn't posted anything there is a major unforced error. If nothing else it was a way to get a direct line to him post Twitter ban.
There's another flip-side to this which is particularly important towards the more extreme end of the right wing - some people want to go where their enemies are. That Twitter allows you to jump right into the middle of a discussion and directly engage with or antagonise those who you dislike is a big draw. For those into reactionary politics, being siloed away in a little safe zone with people who agree with them isn't particularly gratifying.
edit: I agree with your comment btw, I just wanted to add a little something to it :D