In the 4th season of Billions, after founding Mason Capital we see Taylor's new COO Sara Hammon, played by Samantha Mathis.
Did Billions explain how Taylor hired her?
The only "explanation" we get is from Taylor who says
"It's a big part of why I asked Sara to become COO. Her reputation, first as Chief of Staff for the Supe*, - then in Silicon Valley."
* I'm assuming this is the Superintendent of the Naval Academy at Annapolis as that institution is referened earlier.
The implication is that Sara was headhunted for the role of Chief Operating Officer but no doubt more information will be come available later in the season.