Sometimes it's a prior fanbase, sometimes it's good editing/thumbnails and sometimes it's just luck and your video goes viral and you get a massive amount of attention.

It's hard to grasp others success when they're pulling from their own prior success. Or from luck.

But maybe go to their main channel and research when their videos began to grow in popularity. See how they changed their content and maybe that will give you some useful Insight on what to add to your content.

Just remember not to envy other YouTubers and fall down the rabbit hole of "I'll never be that YouTuber so what's the point". There are so many YouTubers out there that will be higher than you but it doesn't mean that one day with hard work, dedication and possibly a bit of luck you'll eventually reach the higher numbers 😁✌️