it's not so much that he appeals to them, but that he's the only viable anti-war candidate. a good portion of the religious right -- well, the ones who don't think he's the anti-christ or who think us bombing brownskins is the only way to secure the rapture -- find the war pretty disgraceful in terms of their beliefs. also, the war draws its meat fodder disproportionately from the bible belt and poorer areas of the US, and some measure of the thumpers want their boys back, and have jiggered their biblical perspective on us politics to endorse that. lastly, obama's publicized religiosity has had one positive effect with these voters: his christianity seems sincere to them, unlike that of hillary and mccain. (my in-laws like him for the last reason.)
also, the religious right REALLY REALLY hates mccain, and REALLY REALLY hates hillary. obama is their only option!