Let's be brutally honest here.
Bill's hiring practices are controlled by his own unique criteria that other teams don't consider, and because of these factors, available options were few and far between.
BB's hiring criteria in order of preference.
1) Blood relative (Sadly, Bill ran out of kids)
2) Relatives of Friends of Bill (Unfortunately, more FOB spawn are leaving than coming in-----a FOB Net Loss)
3) Recently terminated NFL coaches with Patriots familiarity with offset language within their contracts that allow Bill to pay consultant salaries while receiving coordinator services
4A) Assistant coaches who agree to fulfill contracts regardless of interview requests by other teams for elevated positions.
4B) Assistant coaches who won't demand additional salary or title despite elevated duties.
5) Interns exclusively from D3 colleges who were college mates of existing coaches
It's a very narrow applicant pool and Bill opted for #3 despite lack of pertinent experience in their new "consulting" roles.