She was a cop.
A professional provocateur with a simple directive: disrupt, isolate, and marginalize the capable individuals.
This fingerprint was all over her. For instance, that she would neglect to include conference participants whose views offered workable solutions to problems under discussion. Or, that she would "misplace" discussion submissions, typically blaming office interns. That she used her personal relationships to create acrimony; that she spread false and debilitating stories about individuals who were potentially more competent than average.
She had no movement experience to speak of, but was ambitious, and because she spoke well she was singled out by a singularly inept leadership for positions of responsibility.
How is it that the leadership were so blind? More importantly, that the rank and file were so blind?
It's not mysterious. It's a symptom of the legacy of generations of defeat - a legacy which promoted specific narrow leadership qualities, to the detriment of the project, until the leadership consisted almost entirely of capable public speakers without organizational talent or strategic insight, and the membership accepted this as the norm.
Rumor has it she bought a house. Where'd the money come from?