Why did they have to do this when jpow is already retiring in another few months?

Trump Weaponizes DOJ Against Powell In Desperate Attempt To Rig Interest Rates
byu/DumbMoneyMedia inEducatedInvesting

Federal Reserve Chair Jerome Powell is under federal criminal investigation related to the $2.5 billion renovation of the central bank’s headquarters and his congressional testimony about that, Powell said.
Powell said the probe was the result of the Fed “setting interest rates based on our best assessment of what will serve the public, rather than following the preferences of” President Donald Trump.
Sen. Thom Tillis, a North Carolina Republican, and Banking Committee member, said he would oppose any nominee by Trump to replace Powell, and any Fed board nominee, “until this legal matter is fully resolved.”