The Trump was going to more fully embrace QAnon was overdetermined. He's a narcissist, like all cult leaders, and having a bunch of people set aside common sense and self-interest to follow you is like a drug to narcissists. https://www.salon.com/2020/08/20/trump-embraces-support-from-qanon-they-like-me-very-much-and-love-america/
The only reason Trump went most of his life without being a cult leader is because he's lazy and disorganized and, frankly, a coward. (Most cult leaders are unafraid of confrontation — a skill needed when, say, telling men in your cult their wives are now your wives.)
Trump lucked out. For political reasons, a cult formed around him, without him having to actually do the work of cultivating them or creating an elaborate and baffling theology for them to obsess over, which is a tool cult leaders use to alienate followers from the outside.
It helps that the Republicans spent years investing in a right wing media that trained millions of Americans to believe bullshit. That sort of thing softens people up for cult recruitment.
In this way, Trump is following the path of David Koresh, who didn't build a cult up from scratch, but instead leeched onto the Branch Davidians, who were already a marginalized Christian group that was on the precipice of being a cult, and needed only a gentle push.
It's not an exact analogue. Koresh wasn't lazy and he wasn't a coward and didn't hide behind minions to do his dirty work for him. But I think it's important to recognize that the loss aversion fear narcissists have when there's a threat their cult will disappear is absolute.
The other thing about cults to understand is their followers are often trapped by the common and very human habit of throwing good money after bad. It's hard, nearly impossible for some, to admit they've made a mistake. So they hang in, protecting their egos over their lives.
Look at this woman, for instance. The rational thing to do would be admit she was wrong and value her own safety and her children's lives over loyalty to Trump. But for many people, the pain of admitting you were wrong is unbearable. https://twitter.com/revrrlewis/status/1296419741683286019
This is how cult members find themselves drinking the kool-aid or setting their own children on fire. By that point in their commitment to the cult, the sunk cost fallacy rules their lives.
They've given up their dignity, their money, their family for this cult, all to hide from themselves that they made a mistake. To admit that truth now means admitting everything they gave up was for nothing. Many people would die rather than admit they fucked up that badly.