Hi! My comic has ~130 subscribers -- it took me six months to get 100 subscribers here, and on ComicFury (my first host) I still haven't reached the 100 mark. So I'm not popular, but at the same time I'll admit I don't put very much effort into getting an audience.
I owe much of my exposure to the several times my friend promo'd me; otherwise, I rarely ever advertise, I'm rather quiet when it comes to socializing/networking, I sorta popped out of nowhere with my first longform webcomic, and I've been on a few hiatuses already because of school. :B These factors are not very conductive to overnight success.
Don't be discouraged; normally, it takes time and dedication to getting your stuff out there. If I can get this far by being a recluse, then you'll surely do better by putting more effort into it than I do.
The people who seem to get a large following seemingly overnight often have a fanbase off-site or on another one of their past webcomics. There are artists who have attracted people with their portfolios, and so when they hint at an upcoming comic and begin posting the comic they've already gathered a lot of people eager to see it.
Things like "Trending" and "Popular Now" are chance encounters -- I got on Trending once simply because someone happened to "Like" all 30-40 pages of my comic
so people get on it for all sorts of reasons, and then that leads to more exposure and more subscribers, especially if the comic/premise is attention-catching. It's sorta like viral videos, i guess, in that it's unpredictable what will suddenly gain a lot of attention.