This article claims we are being gaslighted! What do you think?

I am new here so I am hoping someone knows the answer to this question: how does the President's impeachment trial in the Senate impact the upcoming implementation of the Insurrection Act. If I understand correctly, the President leaves office, the military takes over and prevents Biden from being President. There is an interim period while the military will take charge of the country. The US is then reformed as a Republic and Trump takes over once again as President. But what about the Senate impeachment? Is it no longer valid? It seems that the Senate is back in session on the 19th at which point they could conceivably impeach Trump, and yes I know that they want a trial and all that after the 20th, but let's just say the Senate still has that option. Doesn't this tie Trump's hands until the 20th? Anyone know the answer to my question?