I think Jon's mistake was that he thought he could do politics. He could be a political comedian and when you enter that realm you really need to be on your toes and when you assume certain positions you lose connections based on that especially nowadays. The guy was still fairly young and thought he could do it but if you make pro-Trump jokes and bash Hillary you suddenly find yourself not being invited back by Disney to work on another promo of their BS.
I don't think Jontron's goal was to be a political comedian, but rather that a he was friends with people who were.
Jontron appeared in a few videos with the likes of Count Dankula and Sargon at the time they were at the heigth of their popularity, and the former had their big court case. Jontron's interest in that community always seemed to stem from the apparent attacks on freedom of speech.
I think when he got invited to Destiny's channel he was expecting the same calm atmosphere as when he was invited by Sargon. Where people did sometimes have political differences, but they didn't debate with the intent to smear the other side. He came to destiny unprepared, and paid dearly for not looking deeper into who Destiny was and what he does for a living.
Jontron also came off as a guy who has political views that lean right, but hasn't looked to deeply into why, just like most people regarding politics.
He believes unrestrictef immigration is bad, he just doesn't have the statistics at hand regarding how it affects people who are already citizens. For Destiny open borders is good because open borders creates the most wealth, he has proof that it creates the most wealrh, at least short term, and nothing else matters to Destiny.
So Jontron fumbles when asked for sources, he fumbled when presented with the argument that all the institutions are racist, abd he fumbled when his own ancestry was used against him in when it came to multiculturalism.