Being a niche writer I fit in the non popular category.
Since we're on popularity. I think there's pros and cons to being popular. Once a story is popular there's set expectations to live up to, by my observations as a nobody. The author is restricted to format and routine. Always under scrutiny it seems. Readers can become like nagging siblings for updates and so forth.
On the non popular side, the books tend to be highly original and well written because there's more freedom for expression and development to make it more of an art form. The problem here is that it's all fancy words if no one wants to read the story. Mind as well call the book page a virtual paper weight. Most of this could be due to a few things: bad timing or luck, theme too complex or far fetched, zero discoverability and site support...
I think what makes a story popular is luck, management support, environment factors and easy enjoyment. If readers are able to get past the shoddy grammar to enjoy the story then that negates any lack of quality standards. A reader has adapted.
I could be wrong on all this. It's based on my observations and experiences, so subjective view.