I brought this very topic up with a counsellor recently.
My point of view was that my parents chose the JW belief system primarily because it matched most closely with their own world view and the world view they were raised with, which included intolerance for dissenting opinions and shunning people who did not meet their expectations. It gave them a sense of validation for deeply engrained attitudes and behaviours from previous generations.
In a sense this scenario breeds a "man made God in his own image" dynamic.
The counsellor agreed with my evaluation of the situation.