The argument that no crime has to have been committed is in opposition to the Constitution. It's false and an argument used by the Democrats and those opposed to Trump to justify a political impeachment that had no basis as a crime, which is required.
The constitutional phrase says impeachment is for :"...Treason, Bribery, and other High Crimes and Misdemeanors." The text uses the word crimes. What could be clearer? It also compares High crimes to Treason and Bribery which are crimes. These are serious offenses and crimes that could lead to execution in the case of Treason. Sure, Congress can do what it wants. That doesn't mean they are conforming with the intent and specification of the Constitution.