I don't think it's odd, Lesnar did the same thing he did against Carwin...rush the opponent and hope you land on top to GnP. Only problem was Cain trained all day/every day for that and popped back up and punched a depleted Lesnar's face in. If it went to the next round, Lesnar could have recovered but not with 3 minutes left in the round. Lesnar's got heart, but not 3 minutes of total ass whooping heart.
Big Nog has been through too many wars, he's broken. Lesnar doesn't like getting punched, he curled up and got beaten up. It happens when you don't train for worst case scenarios.