Terry your question borders on the stupifyingly-obvious: Why have all predictions about END TIMES been proved false? Because no such end has occurred. Duh!
But wow what am amazingly detailed overview of the desperate gullibility of those who adhere to the Christian-inlfuenced religion! Has any other major religion besides Christianity been as obsessively hooked into the hysterical need to wish the world would end? The idiots who run the Watchtower are far from alone - there are sooooo many contemporary and historical Christian groups who have whipped up lots of fear and cash about the imminent end. My maternal and paternal grandparents alike peddled this stupidity from the 1920s and 1930s respectively - and individually went to their sorry earth-bound graves with it. I too will follow them one day - but at least I've divested myself of the need to childish Christian belief that the world and/or its system would end.