You guys gotta quit listening to the GOP politicians on the impeachment process. They keep muddying the waters and combining everything together.
No. While there were some freshmen Representatives who called for impeachment shortly after he was sworn in, Pelosi knew that they didn't have anything (yet) that was impeachable. That is why she never brought it up before now.
The impeachment process was started when the whistleblower reported on the Ukraine phone call. Pelosi looked at the allegations and decided that now there was something that he could be impeached for.
The House then held their investigation. No, there was no trial because the House isn't responsible for that. After they had held their investigations, then Pelosi called for an impeachment vote and they voted to impeach him.
McConnell isn't helping matters by saying that he is fully coordinating with the WH, and will not be an impartial juror. Pelosi is now saying that until she can get assurances from the Senate that they will hold a fair trial, she will hold on to the articles of impeachment. If a juror in any court in the country told the judge that they were coordinating with the defendant and wouldn't be impartial, they would be thrown off the jury.
As far as the trial? When they figure out the rules and McConnell agrees to give a fair trial, then Pelosi will give them the articles, and the trial can begin.
No. Trump hasn't been denied due process because they haven't set the date for the trial yet. And, the only branch of government that can do the trial is the Senate. If you want to blame someone for holding up the process, blame McConnell, and his statement about not being willing to do his job.