I think that JDubs are so gullible because they can't handle reality and are fully invested in a future paradise earth where there will be no problems. I hope they can cope with the 1,000 reign of Jesus that will have a ton of more problems than what they have now.
They may be gullible also because they like not having to think. They are told what clothes to wear, what to eat, what type of movies they can see, where to go on vacation, what type of car to drive, what to answer when answering during the Watchtower study, what is permissible sex for a married couple, etc.