Players, quality star players, need a coach they can respect. They need a coach who can control the dressing room, a true/real/authentic leader, someone who inspires confidence.
Imagine you have Giannis and Kawhi on a team being coached by David Blatt for example. Yes, Blatt is a decent coach, but he isn't a caliber coach. Sarri is decent, if you're a mid-table club, with different ambitions. If you're a European Juggernaut, you don't hire a Chain Smoking Cancerous Clown.
Ronaldo, Chiellini, Buffon, and even guys like Dybala and Sandro need a coach who knows his shit, a coach who can motivate and inspire, a figure they can look at and trust.