“They did it because the constitution assigns them the role of oversight of the executive branch.”
They were acting out of hatred, not responsibly. The House rushed through and did a poor job, then tried to tell the Senate what to do. The actual charges were not clear and concrete. Charging for overusing power, what does that mean? At that rate any president can be impeached if Congress dislikes any action any president makes.
In this case, Democrats were calling for impeachment for over 3 years. Clearly hatred.