Carmelo and D'Antoni don't mix, they're like oil and water. Anthony is the antithesis of D'Antoni.
D'Antoni wants ball movement, team ball, free flow. Anthony sees himself as the final destination for the basketball on offense, he is above the team. In Anthony's mind, this is the only way to play, so be it.
It will be easier to throw blame on D'Antoni and hire a new coach, keep the jersey sales going, than it would be to be rid of Carmelo.