1) The first and second investor in the anime have nothing to do with the manga. They are tho in the music business. I'm not saying that without a new album you can't make a new season, I'm saying you are loosing money and anime requires them to be made.

2) There wouldn't be basically any fight in the season 2 since it's the Detective's arc. But even still, when you switch style mid-run it's always a disaster. Always. People who loved the first style and anxiously waited for the second season will get massively disappointed, and people who might be into the second style are not getting there because they have to go trough the first style which they don't enjoy.

Let's just assume S2 adapts the more battle shounen part of the manga. If I'm into battle shounen, I would need to watch the entirety of the first season, and get bored by it because there are basically no fights.