It was not a dumb move even though I'm saying this in retrospect here is why. The only two largest challenge threats to Rob were Grant and Mike. He would have lost to either one of them in the end. Therefore he would need to get them both out. By voting Grant out when he did, he made it so only one could have come back from redemption island. Had he voted Natalie off then he alienates Ashley and allows Mike to have a good shot at coming back from redemption island. Therefore the final 5 would have been Mike, Grant, Rob, Ashley and Phillip. To prevent from getting there he would have had to get one of them voted off at the final 5 and it would have been hard for him to get Grant out, though Mike would be gone with no immunity. At the final 4 he would have had to beat a marine (Mike) or a former NFL player (Grant) in a physical challenge. If he failed to do so then Mike and Grant would have won for sure in the FTC. By keeping Natalie he kept his closest ally and didn't alienate Ashley. It also allowed him to vote off whoever came back from redemption island who would be a threat, because the 4 of them were together. It also let me keep the largest goat in Natalie around who he needed to take to the end with Phillip to have a good shot at winning.
