I don't think getting beaten for the entire first round was part of Lesnar's game plan. When he was lying on the ground with his head covered up I think all he was thinking was to hang in there. He's a true competitor, he would have to get knocked out to stop the fight. I think he told it like it was after the fight and he was more humble that he needed to be.
Also, Carwin is one of a kind. He wears 5XL gloves with the most knockout power in the UFC. I don't think there is a fighter out there that wouldn't fold from 1 solid punch to the face. Lesnar did extremely well, he's proven that he's got an iron chin to match his solid wrestling and even Carwin couldn't knock him out when he had all the opportunities in the 1st round. Lesnar impressed me the most with the choke because it shows his evolution as a fighter after only a few fights. I think he saw an opportunity to win the fight and took it, he didn't want to risk wasting another second with Carwin.
The rematch will be awesome. I think Carwin will need to work on his cardio and try and pick Lesnar apart with the punches. Lesnar is still improving though, I think in a few more fights he will be a well rounded fighter.