I agree that impeachment is not to be done lightly.

However, I disagree on another point. You say "... where they state an impeachment is to remove someone from office...". You seem to imply that that's the only reason for impeachment. I believe there's at least one other reason written into the law: to disqualify a person from running for office again.

From the Constitution:

"Judgment in Cases of Impeachment shall not extend further than to removal from Office, and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States: but the Party convicted shall nevertheless be liable and subject to Indictment, Trial, Judgment and Punishment, according to Law."

Truncated sentences often do not have the same meaning as the original sentence. The words "and disqualification to hold and enjoy any Office of honor, Trust or Profit under the United States" may be relevant here. Our government seems to think it is.

And there is a precedent for impeaching and convicting an official after he has left office: https://www.nbcnews.com/politics/meet-the-press/meet-other-american-who-was-impeached-tried-after-leaving-office-n1255516 (the example official was Secretary of War William Belknap).

That article gives a reason: "otherwise, officeholders would simply resign to escape conviction or impeachment".

The most recent impeachment has yet additional factors: Chronologically it happened like this:

1. The House impeached Trump _while_ he was in office.

2. The House delivered the impeachment article to the Senate.

3. Then the leader of the Senate (Mitch McConnell at that time) opted to delay the matter until after Trump was out of office. As we have seen, once the trial started it only took a few days to finish. If the leader of the Senate had taken up the matter when it was delivered to the Senate, then there would have been time to remove Trump from office a few days before his term was up. (I mean, such a timeline is significant according to Mitch McConnell himself -- he claims to care whether Trump is in office or not, as a reason whether a trial or a conviction would be valid.) This is significant (as described after my word "So:" below) because (as even the leader of the Senate later acknowledged):

"[The r****rs] did this because they had been fed wild falsehoods by the most powerful man on Earth — because he was angry he’d lost an e******n. Former President Trump’s actions preceding the r**t were a disgraceful dereliction of duty.

" ... There is no question that President Trump is practically and morally responsible for provoking the events of that day."

So:

Even just a very short time (an hour, a day, or a few days or weeks) of Trump being in office could be very significant. Trump had already provoked the J*** 6 r**t. And he had the power to do lots of things -- such as: give away national secrets, start a war, or try to o*******w or subvert the U.S. gov't in various ways.

So, even _if_ impeachment were only relevant for removing an official from office, it's Mitch McConnell's own fault that the Senate didn't take up the matter when it was first delivered to the Senate and there _was_ time to remove Trump from office by an impeachment trial.

He delayed it until he could claim it was too late. Not that his claim was necessarily valid (I wouldn't believe everything Mitch McConnell says, but some of his admissions are certainly interesting), but it was an excuse that a lot of Republican v**ers would accept, and he knew that. Did he set it up that way deliberately? Maybe it doesn't matter whether it was all deliberate or not, but, having seen how he works, one could guess that it was probably deliberate.

Mitch McConnell's a funny guy in some ways. He delayed the Merrick Garland confirmation process about a year, saying it shouldn't happen during Obama's final year in office, and yet he rushed the Amy Coney Barrett confirmation process in the much shorter time remaining in Trump's term. When asked about this, he said, "You would do it too." So now, after saying Trump shouldn't be convicted in an impeachment trial after leaving office, what do you think Mitch McConnell's going to do if he comes to power again and gets the chance to convict some Democrat in an impeachment trial after the Democrat has left office? I think he would, again, act purely partisanly, without scruples, and say "You would do it too." That's what happens if you let a guy like that have power.

There's also the matter of whether a President should be held accountable for what he does during his final days in office, or, instead, he should get a free pass to do wh**ever, such as to subvert the government, overturn an e******n, set himself up as dictator for life, send out some goons to murder some political opponents, or wh**ever. Well, if Mitch McConnell (the leading Republican in the Senate) is right, Trump _did_ spread wild falsehoods and was practically and morally responsible for provoking the "events" of J*** 6. Oh well, why should we care, he failed that time, maybe neither he nor anyone else will try such a thing again. It's not like he'll ever run for president again ... oh wait, dang, Mitch McConnell could have stopped that, what an unfortunate oversight! And nobody died ... oh wait, dang, some people did die ... well no _congresspeople_ died _that_ time ....

There are other ways to hold Trump accountable for _some_ things, but impeachment is a way to hold him accountable for:
"Treason, Bribery, or other high Crimes and Misdemeanors"
even though some such bad actions may not be punishable in criminal or civil courts. A deed by a public official, which is not a crime, may still be an important violation of the public trust that would need to be prosecuted.

McConnell waited to give the dems time to cool down and realize that there was no chance of an indictment and tried to save them from looking foolish again which in turn makes America look foolish to the whole world. But the damn dems , in their blind h**e for Trump pushed for impeachment just to further blemish his presidency. Resigning from office won't make any charges go away from criminal prosecution . So I feel that part is a weak argument. I'll bet some family member of one of the deceased from J** 6 will file criminal charges against President Trump for wrongful death or some other related charge. We'll have to see where that goes. In these crazy times you never know.
But in normal times the case would get tossed out. As for time lines the storming of the capital was happening while Trump was giving his speech. I don't think he Evan got to the part about fighting. And ample evidence of pre planning for this event can be found on social media . So the r**t was going to happen regardless of what Trump said. Knowing Trump would be blamed. It's sad it has come to this but Trump had to fight the dems and the media every day for over 4 years and still managed to fulfill most of his promises to America. And for what? To be ridiculed , humiliated, vilified? How has Trump's presidency hurt you personally?