Competition is good. Even if we lose so what? We can't win it every time, eventually someone else will win it. At least some more people will want to watch it now. Serie A has been becoming more and more irrelevant for years now. Competition will make it so much more interesting.
For Juve it's also good. If they rivals push Juve for the title, the chances to show up in Europe are also higher. If the league is a walk in the park for Juve, they usually find it very difficult to up their game for those CL nights.