The director of Boston’s DeCordova Museum is leaving his post after 22 years, and while rumors persist that he was pushed, Paul Master-Karnik insists that he made the decision to depart on his own. “During his 22 years at the DeCordova, he led a transformation of the once- sleepy institution. The DeCordova’s current $5.2 million annual operating budget is more than five times larger than when Master-Karnik arrived. The museum’s endowment has more than doubled, to $10 million. In 1998, the DeCordova finished an $8 million campaign that included the construction of a new, 20,000-square-foot exhibition wing.”