Legitimacy is not the question at hand. They used the proscribed process.
This was ultimately a political question and it comes down to a subjective matter of opinion.
But you are correct, it has nothing to do with the justice system.
The prescribed process is to at least have evidence a crime was committed.
Guess you missed that part of the process where EVERY OTHER HOUSE held hearings before deciding on the crimes to list in the Articles of Impeachment.
These clowns once again decided on the crime, then expected the Senate to discover the evidence from the mountain of crap the managers presented.
The impeachment was illegitimate on its face. Fastest impeachment in US history, and it was another failure. How many times before you see that the Dems are abusing their Constitutional powers for purely political theatrics and at the expense of the entire nation? Neither trial had anything to do with an actual crime. Hell, the first Articles didn't even bother to list a crime -- just "Abuse of power". So ambiguous and broad, proving it was impossible.
Now they settled on "Incitement of Insurgency." No witnesses to even bolster their claims that impeaching Trump out of office was even Constitutional. A Senate vote where 47 disagreed it's legitimate at all is not an endorsement. The legitimacy is still not settled, but the Dems managed to shove it through a vote.
Facts are not decided on by majority votes in the Senate. Votes only tally the Yeas and Nays of a bunch of elected politicians who vote more down party lines than they do based on facts.
Illegitimate. No question in my mind. The rush to impeach, the lack of witnesses -- expert or fact witnesses -- and the Dems using fake news as sources for "evidence" tells me this was a railroad job. The witch hunt to "get Trump" continues.