Motorcycle racing is a business these days. You can't field a team without sponsors (even if you're Valentino Rossi). In order to get sponsors, you have to have a good overall team - one that has a positive image. It's not just about talent. It's about building a complete team that can present itself for the sponsors and further the team. Winning helps this image, but it's not everything. Having a good rider that you can invest in and help mold into that professional image is key.
Rossi has that image thing down to a tee. He's talented, motivated, personable, and loved by millions of people. He's THE face of MotoGP. It's very telling when someone like him has it all figured out and this 20-year old would-be racer comes in and gets let go from Rossi's team. I think Rossi sees this kid as a risk from an image standpoint. No doubt Fenati can win, but if there's constant in-fighting and no one likes him personally, then the image suffers. Sometimes it's best to sit down, shut up, and hang on for the ride. Fenati better figure that out quickly.