I think Rush Limbaugh has the correct take on this.
Even as a world renowned businessman, there are only so many qualified people for these positions you even know, let alone who can be successfully vetted, and then who will take the job.
Just FYI and not bragging, but Steve Bannon asked me if I wanted to head Library of Congress. I said “Hell no.” I’m not an administrator, and I hate Washington. And that’s a nuthin’ job. So you can imagine how very qualified people would be hard to find.
I am NOT comparing Trump to “nazis” but think back ot 1946. There was a ban on Nazis holding any power in Germany-—yet Patton found he couldn’t even run the water and electricity plants with non-nazis cuz either they had been killed or left 7-10 years earlier.
So, think of the nazis as the Swamp. Unable to find all the “loyal” but smart Trumpers, he had to turn to recommendations from inside the Swamp and that was first and foremost Priebus. But McMaster came with recommendations from everyone: I recommended him, Victor Hanson recommended him, and, according to Bannon, “so did 50 other top conservatives.”
Bottom line, it has taken a while to get rid of insiders and slowly find Trumpers willing and able to do the job.