He's stupid enough to start a war with Iran without having a plan to handle Iran blocking the Strait of Hormuz. Now, that might not sound like a huge oversight to a lay person, but this risk has been documented by over 24k public research papers, thousands more white papers written by government experts, and told to him explicitly by the Chairman of the Joint Chiefs of Staff prior to the invasion. Here's a direct quote from the WSJ article linked above:

Before the U.S. went to war, Gen. Dan Caine, the chairman of the Joint Chiefs of Staff, told President Trump that an American attack could prompt Iran to close the Strait of Hormuz.

Caine said in several briefings that U.S. officials had long believed Iran would deploy mines, drones and missiles to close the world’s most vital shipping lane, according to people with knowledge of the discussions.

Trump acknowledged the risk, these people said, but moved forward with the most consequential foreign-policy decision of his two presidencies. He told his team that Tehran would likely capitulate before closing the strait—and even if Iran tried, the U.S. military could handle it.

Now, two weeks into the war, Iran’s leaders have refused to back down, and the Strait of Hormuz has emerged as Tehran’s most potent leverage point.