I didn't watch the video, but in response to the question in the post title:

It's irrelevant if he did it legally or not. He's not going to be held accountable regardless.

Was it legal for him to ask Russia and Ukraine to help him win the American presidency by sabotaging a political opponent?

Sure, the Justice Department can conduct an investigation into collusion with Russia in 2016 and obstruction of justice afterward, but the end result was that it's irrelevant whether he's guilty or not since a sitting president cannot be held accountable.

And sure, the House of Representatives can start an impeachment process for him using the threat of denial of American military aid as a device to compel Ukraine to attack another political opponent in the 2020 election, but the end result is that legal or not, he will not be held accountable by a Republican-majority Senate under the judgeship of a Republican Chief of the Supreme Court.

So, is it legal that he assassinated a senior official of a country we're not at war with? Again, it's irrelevant since he will not be held accountable.

Republican Donald Trump is above the laws of the United States and above democracy altogether.