But why? Politico delves:
Sources familiar with the East Wing, who asked not to be named discussing internal dynamics, described the first lady’s office as a challenging workplace, where grueling hours and the expectations of a formidable boss intensify the demands of managing a popular first lady’s schedule, image and agenda.Read between the lines.
“The first lady is a lovely woman, but she’s tough as nails, and that can be hard for some people,” said a source familiar with the office. “She has really high expectations.”...
“For whatever reason,” said one source familiar with the office, the first lady’s staff just hasn’t “gelled.”
“You don’t take these sorts of jobs unless you love the principal [figure],” the source said. “And you can deal with a principal who has high expectations when you’re all gelling as a group, but that just wasn’t happening.”