Easily imposed on or tricked
Credulous people can often be easy targets for scams.
Some people are so credulous that they would believe anything.
Napier lived, too, not only in a wild country, which was in a lawless and unsettled state during most of his life, but also in a credulous and superstitious age.
Young children are very credulous with anything that a respected adult says.
Mulder is, if not credulous, at least more open to accepting unconventional explanations for mysterious phenomena than Scully, who persistently fights to find a 'logical' explanation.