Such people are essentially failures at life, and "the truth" gives them another construct in which they can appear to have "success".
Such behavior is not restricted to JWs of course. How many people go way overboard in "Second Life" or other online games, or (God forbid) make hundreds or even thousands of posts a day to multiple internet message boards?
However, JWs do attract a lot of people like that. That's why elders are often so frantic to jump through hoops and/or cause pain to their family in order to hang onto their "privileges of service". That's why pioneers are frequently reduced to tears and deep grief when they have to "come off the list".
Take away those "privileges", and what is left? A dumpy, frumpy, grumpy old man with a boring job, a stale marriage, no hobbies, no interests, and no savings for retirement.