I mean Fukouro isn't exactly the kind of you'd recruit to be a special agent, assassin, spy and for the majority of the arc Spandam was portrayed as ridiculously clumsy, goofy and incompetent with him causing a Buster Call on Enies Lobby itself and other CP9 agents weren't that professionnal or competent either. Though the marines in the same arc weren't more competent or smarter either, and Aokiji too was guilty of trusting Spandam with a golden snailphone with the disastrous consequences we know.
The world of One Piece is a world of stupid people.