(1) China is more sensitive to shipping and oil shipments (and derivatives) than the US. It hurts both but China much more. The US is hurt in so far as high gas price are bad for elections, a small price to pay for strategic advantage.
(2) Iran has a temporary but unsustainable interest in constricting traffic, and it's not the only country who could impose a filter there. The mere credible threat of a strike on shipping is enough to stop it, so other countries basically have an equivalent capability to restrict traffic. And all countries, including Iran, are unable to sustain a prolonged closure. The current situation is an unstable, non-equilibrium situation for Iran and it's neighbors.
Overall, all of it doesn't really matter to the US because simply taking Iran off the supply chain of China is good for them. They spin the narrative about starting the war for a variety of other reasons so that they can justify the pain it inflicts on their allies (Korea, Japan - very dependent on those hydrocarbons too, and EU) and choke China's oil supplies without looking intentional. Last time the US overtly blockaded an asian nation's oil supplies, Pearl Harbour happened.
Which is another reason why China had such a structural incentive to move toward solar power, battery storage and renewables in general while also powering most of their early growth with dirty power plants.
I think Trump wants to be remembered for having neutered the China threat and having restored American supremacy and dynamism, and doesn't care too much about what it will cost at the next federal elections. I think he cares more about his legacy and wanting to be remembered as a historical figure on the strategic level. He's portrayed as being merely a fool with self interested dictatorial tendencies but I think attributing such simple intentions to him is self deception and leads to poor analysis. It doesn't pay to trivialize figures for disliking them or their actions.
Without taking camp here, I'll say that taking Trump for a fool is shortsighted, in my opinion.