There's a channel that I follow called Nicko's Kitchen. He's been around for years. His channel has over 1 million subscribers, but he's losing subscribers daily, and his views are pretty bad too. 800k a month as it stands. I can't put my finger on why, because the guy is really nice and he does some good recipes. Maybe people have moved on, I don't know.
On the flip side, there's another channel I follow called my virgin kitchen, which has just over 600k subscribers, and gets around 1.6 million views a month.
If I knew the secret as to why, I'd tell you but I don't lol. It's just interesting what makes people stay or go. I think with cooking channels, providing useful real world recipes is a good idea, rather than giant chicken nuggets and whatnot. I mean they might be fun to watch but, are you going to make it?