Easy. Who has more money? It's called "deep pockets". If the other party in the altercation has few or no assets (think "you can't get blood out of a turnip"), you go after someone else, however minimally involved in the matter, who DOES have plenty of assets. Happens every day in the legal system.
Yes and no. It would largely depend on who is eventually seated on the jury. There are a LOT of people in the Orlando area who view WDW as being the ogre that destroyed their little town atmosphere, the monster that devours the "little people", and as some sort of uncaring corporate devil. On the other hand, WDW employs over 60,000 people, most of them locals, who have family and friends in the community. While no plaintiff's attorney in his/her right mind would agree to having CMs or their family or friends on the jury, it can happen. And the defendant's attorney certainly wouldn't want any WDW-haters or disgruntled former CMs on the panel. Ideally the jury would be made up solely of folks who 'have no dog in this fight', but this isn't an ideal world, is it?
Although I totally disagree with the tactic, I suspect (like many of you) that Disney will take the easy way out and settle out of court, probably with a condition that the plaintiff never return to any WDW facilities.