You know, many of them are "smarter than your average bear boo-boo."
there is certaintly something to the aspect of the JW culture which reinforces the idea that one has "the truth" and knows most of the answers to the big questions in life. If one has the truth and knows most of the answers to the big questions in life it is almost a given that they will develop a mindset of superiority over others.
This combined with other cultural aspects such as the Us. vs. Them and Black & White viewpoints tends to similary reinforce a notion of superiority.
Like a lot of people say," A little knowledge ( about any given subject ) can be a dangerous thing." Witnesses point to the Bible and their years of studying- guided by the mind of God ( Governing Body )- and will divulge to everyone to what God is thinking.
Because their self esteem is flagging to such an extent their only other option is put other people down with their know it all attitudes; its almost like a defense mechanism for them too....if they accept other people as equal in terms of say intelligence then they have to accept that anothers view counts for something and this is too difficult.
I remember an elders wife asking me some years ago about what I had been upto in my absence; so I told her that I was at that time in the process of studying law; instantly she reacted in a defensive manner saying 'a posh job and career doesnt count for much with me at all, I am not impressed, and neither will Jehovah at Armageddon' which was just as well when I retorted that I hadnt set out to impress either of them.
Its typical passive aggression; they have got to try and batter you down and make out that they know best or belittle any semblence of success outside of their parameters of the societies framework.
The cheeky witch needed legal advice last year too and was most horrified when I enquired as to where I could send the fee note...the look on her face was priceless....wish I had caught it on camera.