Yes, Zimmerman didn't have to do anything in the criminal case, it was entirely up to the DA. But the standard of proof in Civil Court is much LOWER than Criminal court. As the Judge in the Civil case I was on put it, "in civil case, the plaintiff just has to tip the scales of Justice a hair in their favor to prove their case"
From a practical standpoint, if he wins, I doubt the defendants have the money he is seeking. And, yes, while a jury can't consider the attorney in the case, the attorney does have a poor record of winning cases, but a excellent record of getting new facts revealed in the discovery portion of the case. That may be what this suit is all about. Getting information about the criminal case that has not been made public, in the public domain.