Eyes on your own paper. It's the dire warning of teachers the world over, and it can still apply to you no matter how long you've been out of school. When you're an author, you can't worry about what other authors do.
Finding a Market
A lot of authors have no doubt dreamed of writing the next Twilight or Hunger Games, but that's not how it works. You can't force lighting to strike, and you can't make yourself write within the confines of a specific outcome you want to achieve. In short, what I'm saying is this: you can't worry about finding a market for your books. You can't worry about what other authors are doing.
Don't think about what worked for them, or how they managed to find success. Don't look on Amazon to find out what's missing the book market, or what's selling, and how you can rush to fill that spot.
Don't put your creativity inside a box like that. Don't write for any reason other than this: you've got something you want to write. Writing is a passion, so you should only be writing stuff that you love. If you're trying to reach some idealized version of what you think will make you rich and famous, you're not going to be writing at your best.
It doesn't matter what other authors do. What matters is writing what you like to write.