To a Christian cleric pagan cult objects like
the Crom Cruach stone
would have been
nothing more than na bréig-dhealbha "false images".
I think that stories featuring the old deities
would only have been preserved
by the monks after
worship of those deities had died out. Pagan gods
with active followers either would not be mentioned
at all, or would be
mentioned only in condemnation.