The article is kind of unclear and confusing.
I'm checking on airline boards for the reaction.
But, MDW is a terrible airport, and Southwest has some policies that may have led to this accident.
The only thing I can figure is that the autobrake system was somehow set, and because of that the reverse thrusters wouldn't engage. In the meantime, the pilots -- not having the time to figure it out -- figured they would stomp on the brakes.
This also seems unlikely, though. It's baffling.