How is it stupid? Carwin has KO Power and Lesnar hits like a fright train.
Lesnar is the most dangerous puncher when it comes to the ground and Carwin isn't very accurate (like a 10 year old kid flailing a sledgehammer). That sledgehammer could hit Lesnar cleanly but I doubt Lesnar is going to try box with Carwin. Lesnar is one of the smartest HW around now--he knows how to perfectly follow a sound game plan that will neutralize his opponent's strength (see Mir's face). Carwin's strength is a couple of punches at the right distance at the right time. Beyond that, we don't know how good Carwin will be fighting off of his back or how good he will be able to defend a takedown (he's never demonstrated any TDD).
Look, we've seen enough Lesnar at high enough competition to see that he deserves that #2/3 position among HWs in the world. We haven't see enough of Carwin to say that--yeah, he's knocked people out but so has Houston Alexander--in my mind, Carwin is the Houston Alexander of the HW divison. No question about it and if you feel otherwise, just think about what got Carwin to this place right now and think about how you initially thought Carwin could win.
Another factor is Carwin's cardio. We've seen that Lesnar can go a full 3 rounds and that he could easily go 5 rounds. We haven't seen that from Carwin. Perhaps he is the second coming of out-of-breath Coleman or maybe, he can go a round or two. Even though pro wrestling is not of concern here, Lesnar has wrestled in 60-minutes matches in the WWE (I don't watch it but I heard it on a MMA radio up here in Canada). An MMA match>>>>WWE match in terms of cardio but showing that he could go at full pace for 60 minutes at a point where he was close to 310 pounds shows that he'd tool Carwin in this department. If Carwin were to add on even a pound of muscle, he'd gas out on his way to the octagon.
All I see this match being is getting Lesnar's credibility up among long-time MMA fans--Dana takes someone who EVERYONE think will cause Lesnar problems with respect to his strength and wrestling ability. Dana uses this win and another one (Nog?) to build up the claim that Lesnar is the true #1 HW in the world. Then in the second half of 2010, Fedor is signed and we have the fight of the millenium--the one that will rival De La Hoya/Mayweather in terms of ppv buys.