Wow, you're very dramatic aren't you? Is your entire life like a movie?
First of all, Donald Trump was not the POTUS during that interview. Nobody really thought he was gonna win until he did (oops). If youre gonna try to blame Jimmy Fallon and his show as the reason for Trump's win, then I don't know what else to say to you. Did it contribute? Well, sure, but anytime a person is running for POTUS and he/she receives exposure, that will obviously increase their chances. The reasons for Trump taking office are far more deeply rooted in your country than late night television.
Second of all, Donald Trump is a celebrity. He has been a TV personality for a long time, and he had been on Jimmy's show many times prior to that interview. He's a character, a clown, and gets good ratings. I don't recall Fallon ever endorsing Trumps disgusting rhetoric, and until he does, I don't think you should be putting words in his mouth.
Third, you imply that people are incapable of thinking for themselves by stating that he "potentially legitimized" Trump. If the American population take their cues from Fallon's show, then you are all in far more trouble than you think. It's a fucking late night TV show. It's supposed to be dumb, silly ass entertainment. And you're worried that a show like that may have "legitimized" your president? That's insane.
Lastly, and this one is really gonna get under your skin, but not all of Fallon's audience are democrats or Hillary supporters. Some of those viewers are republican, and they have different views than your own, and not ALL of them endorse Trump's hateful rhetoric like people claim they do. Fallon may have brought Trump on for that reason (outside of their prior relationship and history on the show together) because he acknowledges that he has a diverse audience. Again, MAYBE, but this is all pointless speculation. I'm not going to judge a man and wish him failure because he had a guest on his show that I do not like. If I were to entertain you though and speculate about Fallon's beliefs (which is pointless) I would say this: Fallon is a lighthearted goofball who is paid to be silly on TV. There are no patterns of behaviour or prior acts that are indicative of him holding hateful ideas. If you are gonna generalize Trump's beliefs onto Fallon because he was on his show, then you must follow that same logic and say that about anyone Trump interacts with. You must also say that Fallon adopts the beliefs and ideas of every guest he has on his show. This is crazy, but some people think this way.