This is my worthless opinion:
Ross sits with Marino during home games. Marino, during games, tells Ross that Tua can play, but Tua has not been given the tools to achieve his greatness. Word is out that Marino, and Grier, believe in Tua. Ross respects Marino's opinion. Ross takes it seriously.
Ross then gets word that Flores is difficult to work with. Flores is also not an offensive coach that would prioritize Tua's development.
These two things add up to Ross deciding:
An offensive coach is what is needed to get Tua to be great.
I'm thinking they interview Pedersen, Bienemy, Daboll a bunch of others. Wouldn't surprise me if one of these three are it.