The advantage of youtube is that it's user generation and low barrier to entry allows anyone to produce creations that are targeted to niches so specific, people would be unwilling to make something that targets them due to the lack of profit, if they are even aware of the existence of said niche. It also means that said creations can be made relatable to specific groups.

Things like parasocial relationships also apply, where we watch someones videos in order to get to know them to the point you may unintentionally believe you are friends with them, Something let's players, bloggers, streamers and podcast/radio hosts all are able to effectively exploit. It probably helps that most start off being relatable to there viewers due to there similar (and often worse) economic status.