We never know if Fabio can be success or not because he never have the opportunity. He could be the next Alessandro, Daniel Lee or Demna. Bring star designers to big brands not always work, we seen it with Raf for Dior & CK, Riccardo for Burberry and Hedi for Celine. Just because a designer with more exposure to the public doesn't mean they will sell more. Hedi still struggle re-create his YSL success despite all the investment LVMH pour into him.
Raf want to sell, that why he took all these jobs. But the reason why he failed because it's feel like he always designed his clothes from an ivory tower totally detached from the core clients of the brands that he work with. He wanted to modernize everything that he touched but instead of bring sophistication and simplicity he just added too much details and make it complicated and impractical. People buy clothes because they want sophistication and elegant not to look complicated.
At Dior, beside his debut couture almost every offerings didn't work because his ideas of feminity is just too contrived, it's just doesn't work for Dior woman because you can inject your POV into Dior but it's always have to be root in true feminity. At Calvin Klein, again he have to try hard and change the the line from "collection" to "205W39NYC", everybody can remembered CKC, 205 it's pretentious and complicated. And he neglected the clients that buy CKC because the line designed by Calvin Klein himself rooted in sexy American sportswear with a touch of luxurious. His weirdly obsession with Andy Warhol, horror and cliché cowboys it the reason for his downfall. CKC line was never about profit, it's there to create an allure for people to buy cheaper stuff. How can you convince people to buy underwear when all you see it's Warhol, accident and horror, how unsexy is that. And again at Prada, Miuccia sense of humor and quirkiness it's been overshadowed by Raf overcomplicate stuff. Why everything have to have the triangle logos in it. And designing at Prada it's tricky because everything have to look like something Miuccia personal wear it herself, and that why Fabio will works because he understand her taste, he help her create what we know as Prada today.