Speaking about my parents who were the ones who joined (I was born in too), what I see is the Wt gave my mother a lot of good things that she otherwise thought she would never get. Hope, literacy, friends, a community, a sense of belonging, a way of using her skills. She was later "blessed" because her alcoholic violent husband also joined.
Many people are lonely and need a sense of community and belonging. My father didn't have opportunities to learn and study anything and in came the Wt to bring him the opportunity to learn something and be able to teach it to others, and even have a position of leadership.
Other people I know have joined as a way to stay away from drugs, or to escape (or have an explanation for) bad family situations.
Using terms like dumb or lazy, I think is a little misleading in most cases, though I do know that there are people who love having everything explained and given to them, or don't want to face life on their own. The cult shields them from doing so, and they are happy living that way (or so they seem).
Intelligence has nothing to do with what a person feels or their ability to handle their own emotions. The Wt and other cults capitalize in what other people are missing in their lives at a point when they feel that it's important to them.