To answer your question: Trump told his officials not to cooperate with congressional inquiries. It was amazing. Impeachable.
He attacked judges. Tell me when Dubya did that. Or undermined the Fourth Estate. Daily.
Anything that might have checked his power, he attacked.
The institutions held, but barely - thanks to a few brave individuals in Georgia and Arizona who refused to overturn an election, which cost them their jobs (or soon will) - and next time, who knows.