Napoleon's maxim is actually a post-rational selection effect. When the discussion is about 'we need good generals', you in turn inevitably get sophists who want to muddy the waters of 'what is a good general', since they aren't good, and turning the army (or any other organization) into a bureaucracy and marginalizing good officers via memetic weaponry is the only way they can get ahead in the organization, or just plain congenital spitefulness, regardless of if they personally benefit. Eg, "sure he may have succeeded, but that doesn't count because reasons", "sure I may have failed, but that doesn't count because reasons", "we don't understand or can't comprehend what happened, so we can't account for it". And et cetera.
Mooting the discussion over 'luck', on the other hand, short-circuits this rhetorical process, effectively giving feedback from reality itself the final say in any case, ironically bringing things much closer again to de facto selection for good generalship.