It's called luck, videos get popular depending where YouTube randomly decides to place them, if they appear at the top of the search list for that particular category means easy hits. The same for videos getting related to successful ones so that they appear right to the side of vids with tons of views already.

I actually tested this some years back and reuploaded the same vid a couple of times, it appeared in different places each time. The 2nd time having a better placing. The way YT works is pure shit IMO. I'm not joking, this is why you see crappy videos with a lot of views and get people saying "How tf did this vid get so many views?" etc..

YT doesn't go by quality videos, you have to make those and slowly build up an audience. Fast success on there really is luck based on what i just explained.

@sonicwrecks It's also really a lot about charisma. Some people are great being diplomatic, make their audience feel valued and just have a great hook that a lot of people go for. Take Maximillian Dood for an example, he's the only one I follow because I like his optimism and the way he shares his thoughts and appreciation for his viewers. If you count all fighting games and not just a single one, he's by far the most popular on Youtube and he does really well on Twitch too. I don't agree with all his views, but he's cool about his opinions. Then there are people who go for people like Angry Joe etc., or the tween audience that PewDiePie has. It really comes down to what personality appeals to different groups of people -- and I think it's far from luck. I don't most of these people expected to become popular, so in that sense it's luck, but not if you view it from a birds eye.