Could possibly be Klaus, it does seem since Henry joined Bergkamp's numbers went down quite a bit but it's possibly age catching up with him at that point. Could also be because we had so many goalscorers in the team that he was probably not needed as much in the box rather than feeding our other attacking players. Bergkamp was a genious and a master at adapting to suit the team's needs so he probably adjusted.
Needless to say, as you mentioned, he was an unbelievable finisher given half a chance and transformed from a great goalscorer at Ajax to a scorer of great goals in his later time with us (not taking away from the great goals he scored as a great goalscorer that is).
Shit, remembering him honestly makes me a bit sad.