In 1968, the GA Democratic party wanted Wallace to win and worried he couldn't win a runoff, so they changed the rules.
This is the correct answer.
I can't recall whether GA had a presidential runoff requirement for the entirety of its history prior to that (if so, it was done via EC by the General Assembly), but it was definitely done away with for presidential elections in the run-up to 1968 for the above-mentioned reason. As a fun side-note, they left it in place for all other races due to Callaway in the 1966 gubernatorial race being the first R to win a plurality post-Reconstruction; the "runoff" at the time was handled by the General Assembly, who of course chose Maddox.
