according to the article, it is customary for appointees to submit their resignations at the end of the presidential terms, to allow the incoming administration to start with a clean slate. Schwartz began serving under Bush, and Obama has declined his resignation twice. The Trump transition team made the decision to accept Schwartz’s resignation when he submitted it this time.
I heard that today. The transition team told him he could stay on through the inauguration but he decided to be a drama queen and take the story to the WaPo.