There was no investigation. That would have been the Senate's job, and the majority chose to abrogate their responsibility.

What? The Senate sits as jury.

The way I see it is the majority in the house abrogated their responsibility.

"The Senate shall have the sole Power to try all Impeachments." They chose not to, so no witnesses were called, no facts testified to under oath.

I think I see the point of separation of understanding.

The House conducted a House investigation to determine if there were grounds for impeachment. They concluded there were, and they drew up articles of impeachment.

The next step is the actual impeachment trial, where the Senate has the authority to compel witnesses to testify under oath under threat of contempt. The House lacks this power over the other branches of government (i.e. as White House counsel explained, they would not comply with any members of the White House staff being called before House committees).

But since the Senate chose to call no witnesses, no witnesses were compelled to testify under oath in an impeachment trial.

I believe that since there was no support for the impeachment from the House minority, the Senate majority was justified in their action. If the roles were reversed for all parties, I would not find the outcome any less expected.

There's certainly precedent for impeachment to break along simple party lines (for both parties; a similar thing happened with Clinton), but that doesn't mean it's not abrogation of responsibility when it does.

There's a reason Congress has the approval of only 1 in 4 Americans polled.

31 Democrat congressmen joined the Republicans in Clinton's impeachment. Some of the Democrat senators also voted to convict. [1]

Not as exactly clear-cut as this time around.

1. https://en.wikipedia.org/wiki/Impeachment_of_Bill_Clinton#:~....

Good point. I agree Congress was notably less partisan during the Clinton era.