I hadn't noticed that it was so close. It is a bit surprising, but MS may have been much more disillusioned with the Democrats already by this time. They gave the largest percentage of popular votes to the GOP of any state both in 64 and 72, and hadn't gone to the Democrat in the electoral college since 56.
This mostly, plus also I think the Ford Campaign really targeted this state, along with Texas, Oklahoma, and maybe Louisiana. I remember watching an ad by Senator Thurmond saying that Ford was more in touch with the South than Carter, which I'm guessing they ran in those particular states.