He's not a politician though
As much as I hate him, Bill Nelson (being a former Senator) knew how the sausage was made, and was the ONLY NASA admin I've ever seen to successfully push back on Congress.
All the other admins just took the budget cuts and said "thank you sir, may I have another"
Nelson said "alright you're going to remove funds for program X, then I will cancel program X" and all the shocked congresscritters started going "now wait a minute, that's not how it works!!" and he managed to get a lot of stuff reinstated.
He also canceled VIPER when it turned out it was going to kill 8 other programs with its cost overruns. See https://spacenews.com/nasa-outlines-impacts-of-viper-on-clps-lunar-lander-program/
I think Congress is going to have Isaacman for lunch. He won't last a minute.