You are missing the point. No reasoning is needed for DOJ prosecutors to call grand jury investigation. Sometimes it is just to make sure no crime exists. Grand jury has subpoena powers and that helps prosecutors determine if evidence of crime exists. Only after the Grand jury has finished their job, the case goes to court for a judge to get involved. No district judge can stop grand jury creation. Boasburg is an activist judge and he jumped the starting line because of he is anti-MAGA & has TDS.
No, all the Judge did was quash 2 subpoenas that were directed to the Fed Board. He did not shut down the GJ. And, while somewhat rare, GJ subpoenas can be quashed for several different reason, which seemingly includes, “improper purpose.” The Board, not Powell, asked for relief. Usually there would be negotiation between the Gov’t and the receiving party if the subpoena is too “broad” and there would be an agreement as to what would be provided. Here each party decided to litigate. Boasberg used years of Trump’s statements about the Board and Powell as evidence of prosecutorial bad intent/improper purpose and, also, the Government couldn’t describe the “crime” of an individual board member likely acting in accordance to his duties as to a “crime” and so the subpoena quash.
The opinion could be overturned by an appeals court as there is some uniqueness to the case, misapplication of law/fact, and first impression to this Circuit, but Powell’s term could be over by then so aspects of the appeal would be moot if they are “really” seeking his removal. The idea of using prosecutorial power and court proceedings against independent agency heads would be a different matter.