I don't think De Bruyne is a bad move for Napoli. Before anything else, it is a free transfer. And as far as I can see, he has accepted a huge pay cut in his salary as well.
He was earning 24 million euros per year at Manchester City but now it is going to drop down to only 6 million.
Yeah he is more prone to injuries recently but his talent and experience both can still be quite useful.
Of course Conte recruited a player like De Bruyne for a reason and this has been considered. Conte sees that De Bruyne can still be good in the next 2 or 3 seasons. The problem of being prone to injury can probably be minimized by not playing full, what is certain is that De Bruyne's arrival will be better for Napoli's midfield next season. Moreover, next season Napoli will also compete in the Champions League, of course players who have a sense of security are needed in the team and Conte realizes that.He was earning 24 million euros per year at Manchester City but now it is going to drop down to only 6 million.
Yeah he is more prone to injuries recently but his talent and experience both can still be quite useful.
In addition, in a team to win a trophy depends on players who have the desire, experience, and mentality to win a trophy. So Conte saw that in De Bruyne and he rejected the offer from the Saudi Arabian team because he still wanted to play in the Champions League. So with that desire it will certainly produce good performance for Napoli next season. In fact, I think Napoli is very lucky to get a midfielder like De Bruyne, especially for free.