I think he is definitely trustworthy enough to cut programs without regards to his self interest. Does Elon care that there is a lease for a social security office in Franklin, NC? Does Elon care about a DEI program in Serbia? How does cutting those serve some nefarious Musk agenda?
I do think that Musk is in it primarily for the budget cutting for the well being of the American people. I think he also likes the celebrity and I'm guessing the power is a bit of a narcotic, but I think his main motivation is to reduce government spending.