There's a school of thought about the presidency that everything in his branch is under his control. But that's not how the agencies were set up. They report to congress. Why? Because congress represents the people, not the president. But this president believes HE, not congress, represents the people. To him, these agencies all report to him, not congress, and therefore he can fire them as though they were contestants on his TV show.
This isn't conservative thought. Conservatives through the history of this country believed in limiting presidential authority. The liberals want to give the president the power to do anything. The agencies such as the FCC are considered independent because we don't want the president to control the media. That's what he wants to do, and this FCC wants to give him that authority. But I promise you, if a liberal ever becomes president, the conservatives are not going to give them the latitude they're giving this president.
Going back to the constitution, it gives the president the power to appoint, with approval of the senate. Nowhere does it say anything about the power to fire, except for crimes. People he appoints are there for 5 year terms, so they last through administrations. None of the people he wants to fire have committed any crimes, other than being appointed by Biden. The way to fire is kick it back to congress via impeachment. That's in the constitution. This should be a simple case, but of course it's not.