Mike Johnson warning that if Democrats win in the midterms will result in lots of Congressional investigations on every committee reminds me of Steve Bannon saying that if Democrats win, Trump, himself, and many members of CPAC are going to jail.
Or Liz Cheney saying to her fellow Republicans "There will come a day when Trump is gone but your dishonor will remain."
There's certainly ample evidence of illegality and immorality among Trump and his allies:
Findings of the Mueller investigation, including obstruction of justice evidence against Trump's close associates.
Jack Smith report on why he tried to bring charges against Trump over his theft of classified documents.
SCotUS allows the E. Jean Carroll judgement against Trump to stand.
Trump resisting efforts to release the Epstein files as he promised and as Congress mandated. Trump & co. have also sought to redact and dishonestly frame the documents that have come out. Nevertheless, additional documents continue to trickle out due to court orders and Congressional pressure.
Public investigations and document releases sound like a great plan. If Mike Johnson didn't want to investigate violations of US law and the Constitution, he shouldn't have joined Congress and sworn to uphold the Constitution.