One of my Philosophy professors once said, "An education doesn't 'take' on everybody." If these people grew up as JW's, they've been brainwashed since they took their first breath. It isn't easily undone when people are brought up with the "them and us" mentality; i.e., "we" (JW's and other cults) possess the ultimate truth, and everyone else ("worldly" people, meaning anyone who's not a JW, regardless of their Biblical scholarship or degree of religious devotion) is deceived and under Satan's deceptive power.
I commend your friends for being rebellious enough to go to college. I hope they catch the learning bug and are awakened to open-mindedness and acceptance of their fellow human beings.