I'm sure it has something to do with a Central Division championship under their belt. I will admit to only being a fan for a few years. I hadn't even watched a hockey game before then, but I was instantly hooked after going to a game.
Anyway, the Blues have an incredible team. They're young, but have a lot going for them. Most of the key players are back again this year, the coach change last year was a great thing, and they picked up Tarasenko, who shows lots of promise. On top of that, last year's overall performance was achieved with 3 key players (Perron, McDonald, and Steen) being out a combined 120 games due to injuries. They also have a great goaltending duo in Halak and Elliott. If they can just stay healthy they'll be extremely dangerous.