The politics of a coach and his stars are impossible in the NBA. Consider that the coach with the most power and the strongest history of relationship building by far, Pop, still experienced a meltdown of his relationship with Kawhi Leonard.
Stevens was in an impossible position with Kyrie. He was in the last year of his contract, and we can all sit back and say he should have demanded things from him that he didn't demand. What we don't know is if it would have worked, and if it would have tipped him towards leaving town or not.
In the end, even the strongest coaches are captive of the nature of their best players. Management can be behind them, and that helps some, but you have to have the stars that support the relationship, and if you don't, you won't be in change of the teams destiny.
This is why rolling the dice with Kyrie and AD is so scary, because while neither guy is evil, they are both shaky personalities who don't understand how to construct a stable relationship with their coach.
Of course that starting five could win a title, but it will be a group that will be controlled by the whims of Kyrie and AD. Whatever happens, it really won't be up to Stevens, or any other coach that we could bring in, because that only happens with the consent of your best players.
Does anyone think Kyrie and AD will fully commit to that consent?