The flip side is if you weaken the dollar by appearing unstable and displaying hostility to your main trade partners, you get the drawbacks of the weaker currency (reduced purchasing power) without commensurate improvement in the attractiveness of goods to other countries. Some devaluations are more strategic than others.
But the broligarchs don't need purchasing power. All their wealth is in assets, leveraged many times over. Currency collapse is the best that can happen to them.