The National League Central is weak
When compared to their fellow division rivals, the Cardinals have the best record in the division over the last 10 games. The Brewers and Reds are both 5-5, the Cubs have stumbled at 4-6, and the Pirates have been an awful 2-8.
While some believed in the hot starts of the Brewers, Cubs, and especially the Pirates, they all seem more like teams that overachieved to begin the year and are falling back down to their initial expectations, while the Cardinals are doing the exact opposite.
This doesn't mean those three teams cannot win the NL Central this year, but I don't think they are going to give the Cardinals as much trouble as they'd find in the National League East or West.
A weak division allows for a team like the Cardinals to climb out of the hole they are in. Crazy enough, they are only 7.5 games back of the division at this point. They could very easily cut into that lead significantly before the end of May, and have all summer and September to cover the rest of their deficit.