I have several things that interested me and became popular, but I didn't hate on the new fans. At most I sometimes missed the feeling of having this thing that was a bit obscure and in case of channels on youtube, the intimacy of interacting with the creator and other subscribers was nice. But I can't hate on something I like becoming popular.
As for concrete examples, I do remember subbing to this small gaming channel with 9000 subs called Markiplier back in the day.
I subbed to OKI Weird Stories when he had like 600ish subs.
I subbed to Creepcast before it had any videos on it, but that one is cheating since both meatcanyon and wendigoon were already very popular. Still, it's been a bit nuts seeing the podcast explode in popularity. I even know people irl who listen to it.
Currently I follow a small channel, also podcast format, called The Daydream Arcade that focuses on reading reddit stories, but the hosts are two friends, who bring some warmth and personality to the format which is nice. For me, I stick around becuase I really like their friendship and their personalities. I'm also a older than the both of them and feel a bit big-sister-protective of them. I want them to grow and I believe they will because they already have 4500 subs compared to the 900 they had when I found them, but also don't like the thought of them reaching a point of popularity where the mean assholes come crawling to tear them down.