That guy is essential the head of the Republican party, which controls half of Congress and holds a majority of seats on the Supreme Court. When he says jump all of the other Republicans ask how high, while they all try to figure out ways to 1up each other to please him.
So when he speaks, he indicates what he wants to happen which telegraphs actions of all of his sicophants. So if he says “torpedo the border bill” it gets canned. If he says IDGAF about NATO, you can be sure China and Russia see an opening they can exploit.