Question about Columbia MD show

This was my first time seeing Mumford and Sons performed and they did not disappoint. I did leave with a couple of questions:

1. Why were the guys cracking up at the end of the Boxer?
2. Before The Boxer and again before The Cave Marcus looked at Ben and Ben shook his head as if he didn’t want to play anymore and was ready to call it a night. Was he for real or is this a bit?