Especially when you need the Senate for confirmation of appointments. There’s a point where one’s enemies start talking and the longer they talk the more likely they are to start coordinating. Trump’s advantage is that the Senate is composed of 100 egomaniacs, coordination will be difficult. But not impossible.
Removing Sessions would not be Trump’s best move, especially if he replaces him with Giuliani. While that would undoubtedly make Trump more comfortable, there’s an awful lot of New York showing up. As long as the productivity level increases, he’ll be all right, but people who do government for a living are incapable of making a living via market-based activities. The only way they can make it is to insert themselves into other people’s lives and demand a cut. Back them into a corner and they go passive-aggressive on you, and you will at least have to divert time and resources to deal with them.
Who would want the job if he is this way with Sessions?