How did they get the job?
Each office has a variety of staffing rules and requirements, which are oftentimes based on an allotted budget for the specific entity. Typically, every White House office has several commissioned officers (senior staff) and non-commissioned officers (mid-and entry-level staff).
A commissioned officer holds one of three designated titles – Assistant to the President (AP), deputy assistant to the president (DAP), and Special Assistant to the President (SAP) – followed by their office title. For example, employees in the National Security Council could have titles such as Assistant to the President and National Security Advisor; Deputy Assistant to the President and Deputy National Security Advisor; or Special Assistant to the President and Senior Director for Asia.

Each council, or office, usually has only one assistant to the president and one deputy assistant to the president. The number of special assistants to the president varies based on the makeup of each council and how many positions are allotted.
The National Security Council, for example, has over a dozen SAP lots, while the Domestic Policy Council has around five. This, however, changes from administration to administration based on the staffing makeup. The Office of the Chief of Staff allocates the number of available commissions to the various offices.