I see many in the US thinking that Trump is an idiot. No, he is not. He is a blatant liar. The fact that many people cannot believe how blatantly he lies does not mean that he is unaware of reality, means that he knows how to detach other people from it. If you look at him and the people around him as people who lie with every breath that they take for the express purpose of ensuring their own wellbeing at the expense of everyone else, the underlying logic of their actions becomes painfully obvious.
You think that truth and integrity matter. They don't. Once you disabuse yourself of that notion, you are left with the meme and with the story. And while you think that the story is how he is wrong, he does not care because his story is about the things he wins.
Example - the climate. Everything in the US government was bleached from the words "climate change", but he is bent on occupying Canada and Greenland, both places which will be much more profitable when the ice melts. People can continue shouting from the rooftops that there is a climate change and he denies it. While they are busy doing that, he positions himself to profit from the incoming disasters. All the better if he can speed them up by selling more petrol.
Example 2 - government cuts. Will they make the government more effective - no. Will they make his cronies richer - yes, while making other people poor and easier to exploit. Is that a smart plan - no, but he is not the one paying the price, so it is fine.
Example 3 - tariffs. Ask yourself not who loses from them, but who wins when the dust settles and the new trade agreements are signed. And I can bet you that no matter how many american households suffer from stackflation or whatever, the household of Trump will not be one of them and they will get out even richer out of that.
Whether he is an idiot or a "useful idiot" as in willingly helping his shady beneficiaries doesn't really matter, since he surrounds himself with real idiots (main qualification being willing to bootlick the boss) and something will for sure go wrong.
He is a blatant liar though, no doubt. That doesn't really contradict being an idiot.