Ajax's self-confidence will of course be high because this match will be in the Netherlands, in front of their own fans. That's why they're sure to take power. Still, Napoli is not a simple team. They play well away games as well. They're playing really well in their league this year and the Liverpool win really showed that the big teams should be afraid of Napoli. That's why I think the odds of Ajax winning are a little lower.
i think it's mostly because Ajax play really good in the Champions League especially in the last few seasons, it won't be surprising to see them win even with Napoli's incredible performance this season, i mean they are the favorite to win so it's not crazy to see it happen, maybe the bookmakers see something that we don't and they're going to win the match.