There are seven openings as a HC for an NFL team. With at least 30+ suitors, I doubt the coaches are looking at all these aspects. The real key is talent and/or ability to procure talent. If the coaches don't feel they can win with the talent on the team, they will take themselves out of the running. I think the Bills are in a better position right now than they were 3 years ago.
The NFL dream is short lived. If you are a hot Coordinator and a possibility for a HC job, you are going to take it, because you may not get that chance again.