He's pissed off the half of the party that still have holiday homes in reality. Sunak, who is one of those, noticeably banished him to the back benches, because the man's not only malevonent he's useless, even by current Tory party standards. Putting him in power would be even worse than Truss.
Plus, remember, this was an MP stitch-up this time around, and not the party membership. The party membership are insane, which is why they wanted Truss. The MPs actually have to worry about re-election, which is why they rallied around the more moderate and competent candidate, relatively speaking, while everyone else stood down. The candidate they can actually potentially not get wiped out in a future election with, unlike Truss or Rees-Mogg. Sunak did have glowing profiles written about him for his Covid budget measures, after all.