The Board of Governors can remove the Postmaster General with a vote.
USC Title 39, Section 202: "(c) The Governors shall appoint and shall have the power to remove the Postmaster General, who shall be a voting member of the Board. His pay and term of service shall be fixed by the Governors."
You should watch it. Jenny does a great job breaking down what they did right and wrong. And it turns out it was such a monumental project that you need four hours to talk about it fully.
Our attention spans are dropping precipitously, and it worries me.