JWs borrow from the Adventist and put a twist on the scriptures. They did so effectively with sociopathic scribbles of Fred Franz presenting in an assertive way that they had deciphered the meaning of the scriptures particularly concerning the Kingdom. For wayward and weary church goers and curious alike, all that door knocking and good news moved a lot of hearts. Look at what was happening in the world during those early days. Mainstream religion was boring and stagnant. All those rebellious hippies needed somewhere to land.
It is a different religion today made up of captive born ins, prodigal sons and a pinch of "worldly" despots. Nobody in their right frame of mind joins this religion if they have simple internet connection. If they do...they frankly deserve what they get.
A more intriguing question to me is, "why do so many people stop being Jehovah's Witnesses 100%"? PIMI, POMO, POMI, PIMO. WTAF?
Pinch it off.