Expecting a win from this game was something I really didn't put my mind to but I predicted that they were both going to have a goal but I didn't expect a gaol so seeing this now actually didn't come as surprising really. Napoli has not shown so much definition in their performance in recent times and so I had it in mind that at some point Napoli may not have the best performance people may expect of them, but then for this particular game I didn't have any expectations in particular. But I think Lazio is doing great.
This game in most cases isn't easy to win by either team so just like you said "Both teams to score" would have been the correct prediction for a game like this. I too picked the Both teams score. But on the otherhand, most punters will pick Napoli to win because of their form and that they needed to win by all means to keep that distance they had with the second placed team, Inter Milan