That’s not how cults work generally. The leader is the leader because of some charismatic attribute. Most of the followers are followers because they can only follow. They don’t have the charisma to lead the cult. Watch any of his underlings when they deign to interact with people outside the cult. It’s awkward, weird, and usually leaves you feeling uncomfortable. Within the cult they might have somewhat of a commanding presence or ability to hold cultists attention, but they are useless for growing the cult. And that’s the rub. Cults die without new members, especially ones that are primarily made up of the elderly, eschew typical medical advice, and live unhealthy lifestyles.

Add on to that, trump doesn’t seem like the type to “pass the torch”. So I imagine once he goes, there will be a greedy and hateful power vacuum that rips through the republican party (especially if it’s while he’s still in office).