Read her facebook statement and her resignation speech.
The reasons are there. The only thing “shrouded in mystery” are what she is going AFTER her resignation.
I read it and I heard her give the speech. I heard and understand her reasons for leaving, but she gave little to really indicate her future plans. I think we need to let her tell us her next step, not spend all this time speculating on what she may or may not do next. In the mean time, time’s a wastin’ and there is much to do.