Oddly enough, the Speaker of the House does not have its own police force or courts. They are stuck relying on the Federal Courts for justice and the executive branch for enforcement.
When the inJustice Department refuses to enforce congressional subpoenas, even arguing against their validity in court, what course should the Speaker have taken? The House tried by holding many hearings but were able to get precious few witnesses to testify under oath. Without concrete evidence or testimony and without a legal ability to coerce compliance with subpoenas, I suppose the Speaker could get on Twitter and rage against the Deep State, toss out unsubstantiated charges and call everyone who disagrees losers and nasty, but that schtick has been taken.