If you get the idea "I want to write a blog" it seems likely you will pick one of those topics that is impossible to monetize such as an anime or programming blog.
If you get the idea that "I want to monetize a blog" you would pick a random topic and find that a randomly selected topic probably monetizes a lot better than a programming blog.
If you get the idea that "I want to monetize a blog" you would pick a random topic and find that a randomly selected topic probably monetizes a lot better than a programming blog.