I've listened to these long ass videos before, but I must really like the video itself, the message, the topic and the person(s) doing it. I do it mostly when playing videogames that don't require a lot of attention, like Rimworld, EUIV or a football (soccer) game where I can just kinda disconnect, listen and play or have the ability to pause if needed. After all, it's a video, you can take your time watching it, you don't have to watch all four hours of it at once, but rather bit by bit.

And yeah, there's people who really like a well researched video on youtube plagiarism, maybe they like the topic or maybe they like this guy in particular so much they're willing to listen to him for hours, and in this case, Hbomberguy is super likeable. I've had people in Uni willing to listen to a professor speak about I don't know, early Argentinian history for HOURS all while sitting in one place and doing nothing but listening, I can really see people pulling through videos of 4 to 6 hours talking about random shit as well. There's people for everything!