1. Chicago is very unforgiving of quarterbacks
Few fan bases have more passion and intensity than Bears Fans. It is very difficult for a quarterback to come in and perform in Chicago because the pressure from fans and media is enormous. At times, to their own detriment, Bears fans do not have the patience for development. They will let it be known when performance does not meet expectations.
It takes a quarterback with extremely thick skin to come into Chicago and not be fazed by the constant criticism they undoubtedly will receive. Jay Cutler had the right mentality, but like many other Bears quarterbacks, his production was very inconsistent. Justin Fields was built for Chicago. He takes the heat even when the heat shouldn't be his to take. He handles the criticism with professionalism and class. He uses the criticism to fuel his drive for improvement. He was dealt a horrible hand when he arrived in Chicago, and he may be on the move this offseason as a result.
If the Bears move on from Fields, they need to take a long, hard look at the mental toughness of the quarterback they bring in to replace him. Being an elite athlete is not enough in Chicago. A rookie quarterback is going to struggle and will receive immense criticism as a result. If they cannot handle the criticism, the Bears need to look elsewhere.
Not having the mental toughness to play quarterback in Chicago is not meant to be a knock on anyone. It's a city where few have ever been able to do it. It is, in my opinion, the driving force behind why they have such a difficult time finding their guy.