Actually, the most important impeachable offense is Trump's refusal to cooperate or let any Executive Branch employees cooperate with the impeachment proceedings. This flies in the face of our system or checks and balances, separation of powers, and the Constitution. The American Republic is broken irretrievably if nothing happens because of this. It replaces our Presidency with a dictatorship.

This is the real constitutional crisis, unless the Supreme Court tells Trump he has to cooperate, and everybody honors that decision.