I think the LBS initially doesn't realize the pain the WAS was feeling in the M. The pain they feel (real or not) is excruciating... so much so that they took a huge gamble to throw it all way and make a drastic move of leaving.
Not to generalize or be offensive to women, but I think this is the reason that I thought I read where 70%+ of most WAS are women. They are typically much more dependent on the emotional health of a relationship than guys, and thus the emotional impact much greater. I think that "flipped switch" comes when they realize their emotions are going to drive them possibly literally crazy, so they just drop like a stone and go. (My opinion, and I'm not a professional) This is exactly how my W described her feelings: a "switch just flipped".
