What did Trump do to Milo that irritated Milo so much?
Despite all of the opposition against him, the alt-Right also believed that Trump could have gotten the wall built completely and much earlier, and they weren't that happy with Trump focusing on relations with Israel over unfinished business at home.
I'm not certain, but I think some of them thought, despite the optics, that Trump should have called out the National Guard to prevent all the burning, looting, and mayhem done by BLM and Antifa.
I think the alt-Right had an illusion that they were somehow the architects of Trump's populism. Trump's populism was all Trump. If some of his beliefs lined up with the alt-Right it was just happenstance. If his tweets got snarky Gen-Z's to vote for him then that was just gravy. Their votes were not critical to his win in 2016.
Not defending this story and perhaps I’m mistaken, but I seem to recall an interview Milo did with one of the Jan 6 participants (or victims?) in which he seemed astonished that anyone caught up and jailed over the event could have any remaining respect for Trump in light of what Milo considered Trump’s apparent failure to heroically stand up for his own supporters who got caught up in that scheme. He seemed genuinely let down by the shoe thing.