The smartest thing Santa Anna ever did was to order a halt to the cannonade at night, allowing the garrison to fall asleep. There is a great book on the Alamo by Davis, called "Three Roads to Texas," which follows the lives of Bowie, Crockett and Travis.
Yeah, but that was about the last smart decision he made.
Santa Anna seems to have lost interest in the whole campaign shortly after the final assault on the Alamo. I wonder if the 4-10:1 kill ratio had anything to do with that. If true, the anecdotal evidence of Davey Crockett sniping at Santa Anna on a daily basis and knocking off Santa Anna's hat at least once in the attempts to kill him would also have had something to do with him losing interest.
And the dumbest thing Santa Anna ever did was order the survivors to be bayonetted. I sometimes wonder if the story of the Texas Revolution might have been different without the Alamo and Goliad massacres. Taking prisoners is usually a smart thing, as well as a good thing.