I think the idea that Trump is "an idiot" or that he surrounds himself "with idiots" is partly true. But, I just think this description is overly simplistic and, at times, dangerous.
Trump is not an idiot when it comes to his own self interest. He is an idiot when it comes to ruling the country, being a leader, picking people for his administration that will serve their role well. Yes. But the problem is not with incompetence; it is with the misunderstanding of intent.
A "smart" leader would delegate tasks to others that they know are more competent than themselves in a given area of expertise. The "stupidity" of Trump that we define is that he doesn't do this. He actually appoints people that are extremely unqualified for the tasks.
But, this isn't Trump being stupid. He just has the priority of self enrichment and unquestioning loyalty. He isn't trying to govern in the way we are made to believe government should operate.
This DOES result in the administration getting stuck in clearly awful situations of their own making and own stupidity. Iran being the obvious example. But, the intent was never to "free Iran" or remove their nuclear capabilities. The intent was to enrich himself, his family, and the oligarchs of our nation. And, with each mistake the damage of the failure is not taken by them. It is taken by their intended targets and the working class of the world.
Their is no incentive or intent from Trump to rule for anything other than the enrichment of himself and the entire capitalist class. Having competent people that will tell you "no, this will not work" is not helpful when every goal Trump has is masked with a charade.
The military leadership telling him that an invasion of Iran is not feasible, that they will not "do regime change" organically, and that their is no intelligence indicating Iran is developing nuclear weapons; none of that is helpful to Trump. Because he doesn't care about any of those things beyond their use as justification for his own self enrichment and pursuit of feeling powerful.
So, of course he surrounds himself with "idiots" for lack of a better term. Because he doesn't need people that will say anything but "yes sir". He either needs people dumb enough to believe his lies and his justifications; or he needs people malicious enough to understand that his justifications are lies and have aligning self interest of enrichment. That is what his administration is filled with. And I think the later is far more common; though often not as public facing.
So, no, I don't think Trump is stupid. Beyond his obviously declining mental state. And I also don't think he ONLY surrounds himself with idiots yes men. He is primarily surrounded by smart narcissists that know how to play his game. They know that they can enrich themselves and obtain their selfish goals as long as they can offer enrichment for him in return.
Starting a trade war with Canada when gas prices are already a major issue may seem "dumb". But it's only dumb if you're also dumb enough to believe that Trump is trying to be a good leader. Or that Trump and the people in his admin are willing to give up power at some point in the future. They are not. They have told us this endlessly. They are doing such blatant crimes in office that it is clear that they have no intention of letting anyone take power that would hold them accountable.
Edit: I'm using "enrichment" here a lot. This could mean anything from stock market manipulation, control/restriction of resources, genocide, etc. Anything that those that have Trump's ear could want. And most of these people aren't holding a title in his administration. They are the wealthy oligarchs that direct this country.