Why would he not be manipulated into voiding the elections by some means, if it was presented by the right people in the right manner?

Voiding the elections doesn't make him President. To say nothing of the fact that there doesn't exist any means to void the elections that doesn't require enormous personal risk to the President to attempt, and enormous skill by the President to accomplish. All of the actual paths to making him President after 2029 involve such a degree of complete criminality that he risks a firing squad if they don't go 100% right, and Donald Trump is not that kind of guy.

Imagining the President to be under the control of a shadowy cabal of hidden string-pullers is entertaining. That's why so many conspiracy theories follow that framework! It's just good storytelling. But there's no reason to believe it's the least bit true. He's a guy who wants to achieve great things, but is too stupid to understand the reasons why those great things are hard and too conceited to believe that the ones telling him they're hard to do might be right. That makes him easy to manipulate, but only for certain things - a promise of low risk, high reward, and massive personal wealth or glory.

There's no path to the outcome. To use the UG framing:

Step 1: Trump decides he will break the rules in order to be absolute dictator
Step 2: ? ? ?
Step 3: Trump is absolute dictator.

But no one can really explain what Step 2 would be. Something something DOJ, something something military, something something national emergency with the elections. But not an actual path from Step 1 to Step 3.