Revisionist history, more to the story than just the record. Dude basically destroyed his own life and career and peaked well before he had the big name fights. Millionaire at 19 with no guidance and surrounded by leeches couldn't possibly end well.
Also It's not like Cus D'Amato was teaching an unproven fighting style, even if Mike didn't execute on it we know it worked well as fuck historically.
He made a chinny MW the youngest HW champion in history before Mike, bodes well for success in a relatively weak division hypothetically.