Valid points here. It sounds as if we agree there is little evidence of Carwin's true cardio since
a. no one has made it out of the first round with him before Brock
b. the only time he went to the second was after a round 1 in which he threw a ton of strikes (it was his first shot at the belt, too, and that is mentally difficult)
c. none of us know his strength and conditioning preparation for this fight
I would add he was a champion national wrestler, and usually they possesss good cardio.
However, I agree there is a realistic chance Carwin is simply too muscular and large to develop real endurance (much like Baroni, whose muscles are more adapted for weight-lifting contests than an MMA match).
Hard to say either way......... I was merely cautioning against extrapolating too much from limited info and/or a singular incident.
With that said, I liked your post, and I think you may be on the right track by hedging, although personally I wouldn't be shocked if Carwin has learned a valuable lesson and either paces himself well or has better cardio now than we saw in the Brock fight.
For the record, I lean toward Carwin showing better cardio than most give him credit for.
Like we are fond of saying, we will see soon enough!
Good luck to you, man!