they decided to ignore the law and use some newly invented “yes, but does anyone care?” legal theory
Lying under oath in a civil trial over matters that don't conflict with official functions & duties of the president hardly qualifies as "high crimes and misdemeanors", ie, serious offenses of office and in particular those that subvert our system of government.
This is beside the point that Congress was willing to impeach over practically little before yet does nothing to impeach over an incredible volume of lies and subversion of our system of government now.