Well, the dissent had been building for years. Most of the way corps who left would not have had the guts to bail on their own. I did that in 2008 and was happy with obscurity! Most way corps still crave a lectern and some people to admire them and that they can boss around. The exodus actually started with an advanced class grad who mailed an anon. letter to Rosie the RIveter enumerating many typical grievances. Same ole same ole: STS sucks, way mag sucks, everyone is micromanaged, etc. However, Rosie's goofy a$$ thought the letter came from one of her very loyal cabinet men that I won't name. She put him through holy heck for no reason at all. Raked this man over the coals really bad. Other letters followed from a group of way corps and I guess the damn of dissent broke from there. So as time went Rosie, Rupp, and the gang started calling in corps who had signed the subsequent letter(s) of dissent, of course seperated married couples from one another, and interrogated them. They marked and avoided a bunch of corps during this time, which again, was extremely stupid for them since they don't have that many corps to go around any more. A lot of your average followers of course followed their favorite way corps over to revival and restoration. I went to a couple fellowships over in Indy at the urging of a former friend. They were typical twig fellowship formats from the days of old with more room for people to express themselves and such, but same doctrinal package that wierwille pieced together. Same errors, etc. I never went back and that was at least four years ago.
As to what took them so long? Most didn't have the guts to push the envelope on their own but when others started doing it the whole gang jumped in when they felt safe that they could remain relevant to somebody. That's my opinion, but Im pretty sure it's fact based on a broad scale.