There are only a few good reaction channels and many many bad ones. This guy belongs to the bad ones, because he lacks in-depth breakdown of the stuff that he watched. Skylenox is an example of a good channel.
And for those who don't know why reaction-videos are "successful", well, it's similar to what happens on christmas eve. You have presents for your friends and family and watch them unwrapping those. You usually get the feeling of joy when you see other people who are happy and enjoy what they got. Unless you are a jealous person.
That's why a lot of people like to watch other people who enjoy the same stuff and like to talk about these things in a deeper fashion, especially when your friends and family don't have the same taste of media as you do.