I just want to add my 2 cents. A lot of people on YouTube may have meh videos and not much in their channel. Or may be new. You can work 24/7 and wonder why you're not as nearly as good at this guy.
3. things to consider:
1. The person may have a huge channel with lots of viewers and may have migrated to a new one.
2. The person may know a big YouTuber who has been helping promote this person.
I knew of a few people who started YouTube and got bigger than most of us really fast. This was because they were directly related to a person with a huge fan base/subscribers.