As per the usual for this time in the competition, one of the rewards, other than bragging rights for chefs who win the quickfire is immunity from elimination. In "Top Chef" (and let's face it "Project Runway" too) some contestants have taken that as leeway to go big, go bold, go crazy, and some chefs have decided to try to win the elimination round too. (I know this week was also an elimination quickfire, but still.) With, on "Top Chef" the advent of "Last Chance Kitchen" they have tended to feel a little less bad about eliminating a good chef who seemed to have a bad day in the kitchen because, "Last Chance Kitchen" provides the opportunity for them to earn their way back. (And yes, in the end, if you argue for chefs the biggest advantage is exposure, their appearance has already achieved that, so enjoy the nice hotel.)
I don't mean to suggest that chefs who made bad food got passes before, but I think as much as they try to pick the thing they would be least likely to eat again, there are still days where you know secretly, this person had a bad few hours, while this person seems to have reached the end of me wanting to eat their food right now.
So one team had a person with immunity, a person with a strong personality, and a person who sounds badass in the interviews, but seems to default to sous chef mode when on teams. The challenge had a treasure hunt aspect, and two of the members were local which seemed to actually mean they overthought the treasure map, and as a result were last to arrive on a few items. So, the dude with immunity had said I'll take two of these items that don't seem to fit and make something.
The thing he made was not good. And also a boring idea. It wasn't the only bad thing on his team, but it was the worst. So when he said, hey, I'll give up my immunity because I don't think someone else should go home if my dish was your least favorite. And in this case, the judges took him up on it. Again, I think the Last Chance stuff factored in. Otherwise, I'd have been a strong proponent for these are the rules we set up, they don't get to change them. Plus, as Tom pointed out, his team let him take two ingredients they didn't want knowing he had immunity and could create a crappy dish and they could have stopped that. Or tried to help.
In some ways I think Jamie lucks out because next week is the Restaurant week challenge and there's enough problematic personalities left that you could not pay me enough to put up with that. (This is also probably why I'm not in the food industry.) So he gets to go compete one on one and maybe come back later. And in the future, you know if there's another losing team with a person with immunity, the judges may well ask them if they want to give it up.