Despite the disappointment on the faces of the Milan players, they continued to try, but one of Milan's current weaknesses is in the front line, especially in finishing.
But, but, they have Santiago Gimenez. 
Gimenez perform very well when he was in Feyenoord, even he get supported from his teammates, but he still not able to score. 6 goals in 21 match, that's a bad stats actually.
With this result, Milan is having a big problem, they lost against weak team in their home.
Great job for Napoli players!! Even if they have no strong striker, they still could win the match. Sure, Tominay and KDB really made the difference on the match. Having them in the squad, make Napoli scoring 2 goals. I just can't imagine if they are injured, Napoli totally have no strong players in the midfield and attacking line.
They need Hojlund, they can't just rely on this two players over and over, just like you said, injury may happen.The goal scored by KDB was unintentional I think, because he didn't tried to shot directly on the goal post, a good accuracy by KDB, but it's a mistake by Turati.