(Ignoring sloppy writing as the reason…)
Star Fleet seems to like to compartmentalize information. Examples:
At least post ‘First Contact’ they had hints of the Borg before ‘Q Who’ but kept it quiet. Similarly the Genesis device information was on a need to know basis (although probably for good reason). There was also that Voyager episode based around the Omega directive that only Janeway knew about.
Crosspost of what I mentioned on Reddit:
Was this a sly deep cut prequel to 'Wolf in the Fold' ?
Given that both episodes cover the same terrain dealing with "monstrous, terrible evil" and " immortal, non-corporeal entities" possessing people?
'Wolf In The Fold' also ended with the entity jumping and taking over the ship.
('Wolf in the Fold' in the fold was written by Robert Bloch who also wrote 'What Are Little Girls Made Of?', the episode that introduced Korby and Chapel)