There was an old saying in football that the most popular guy in the stadium was the backup quarterback. St. Louis Blues fans took that and turned it up to 11 when it comes to modern goaltending.
The idea is that the backup QB is always popular because people think they just need to be given a chance and they'll shine and be better than the bum that's being trotted out there time after time. That is definitely true for Blues fans.
Ever since the tandem of Jaroslav Halak and Brian Elliott, and perhaps even earlier than that, Blues fans have been at war over their goaltender.