There's usually entire teams involved in preparing these sorts of decks - from content researchers via subject matter experts to designers. So not a single person needs to believe in it all at once.
I think a far better question is: Does whoever is paying for these decks to be prepared believe in them? These decks aren't (always) built for internal use.
I think a far better question is: Does whoever is paying for these decks to be prepared believe in them? These decks aren't (always) built for internal use.