The DOJ served the Fed with a subpoena and threatened Powell with a criminal indictment related to the Fed's expensive renovations.

Powell, rather than releasing the minimal version of a statement that merely disagreed with the accusation, instead released a statement and video that pretty much went scorched earth, saying this isn't really about the renovations and is instead about the Fed's independent control of interest rates.

Historically speaking, this is the biggest direct clash between the Fed and the Executive Branch since the 1940s/1950s.