Which of Trump's promoted conspiracy theories have been proven true?

I don't believe there's been any. But that's typically how conspiracy theories work. They don't need to be proven true to be believed.
Although Ted Cruz's father killing JFK would be a good one to come true.

His headquarters were bugged, everybody laughed at him, and it turned out to be true! The Steele dossier turned out to be fake, the "laptop" was russian disinformation, the pee video turned out to be a lie, Russians and Chinese showering him with money, and none of that was true either!I could get carpal tunnel syndrome typing them all up!

I gave this more thought and came up with the theory from Trump that "The deep state" is trying to keep him out, when he and his handlers are in fact looking to be the true "Deep State". Managing everything for their liking without any reference to law or the will of the people. For that you need control of the courts..You know.. Judges who will delay, defer or sideline uncomfortable "issues" and keep those plebs in line..Sound familiar at all?😷

Dead people were voting. Joan Rivers voted for him after she died.

I can't think of any of them that were proven true.

Well, it's true that we all want to stop him from becoming President, no matter what it takes.