I think Allegri really believed in defending that lead. I can understand that because Zaza would've had little support in going forward but in hindsight yes it seems the wrong move
Well i disagree here.
Morata was perfect for this tactic. He can chase a ball, controll it, keep it, beat defenders, finish a goal.
Mandzukic needs to be at the receiving end of a cross or trough ball in the final stage of a counter. He needs a winger or SS bursting trough. You cant put mandzukic alone up front to deal with counters ,especially against quicker defenders.
Zaza on the other hand, can haunt players as much as mandzukic, but alike morata, is excellent at running behind the defence and has the strenght and sprinting speed to win a duel following a pass over the defence.
This is why you need zaza as your lone forward when you wont get wingsupport. Mandzukic was fine if we also had dybala or cuadrado comming off the bench