The retirement of one of Judith Neilson’s most trusted advisers led to her sudden seizure of control of her $100 million journalism institute last week, according to people familiar with the situation.

Jonathan Teperson, a former Westfield director and chief financial officer for the Lowy family office, had been the director of the Judith Neilson Institute (JNI) through whom the billionaire communicated her opinions to the rest of the board.