I thought my last group interview went really well. I was very comfortable with all the people there. It was like we were old friends. Then, I didn't get the job. What did I do wrong?

It is hard to say, but you may have been too relaxed and too familiar. Even if the construction interview was at a casual restaurant and the people were wonderful, keep in mind that you are being evaluated for your professionalism. Sometimes when we are too relaxed, we reveal sides of ourselves that we would never show in a formal construction interview.