There is nothing wrong with it. Its a good exhibit, and shows that on Large Maps, Deity can be won on Marathon, since Normal speed increases the difficulty.
The question is whether or not (Marathon+Huge)>(Normal+Large). Remember that is is a quadratic increase in land size, not a linear increase.
Does the quadratic growth of map size (coupled with the player Deity expansion penalties) increase the difficulty more than the linear drop from Normal to Marathon speed?
I think Huge is just too much land for the AI's to settle, regardless of speed when put on Deity. Every game shows an entire huge map settled by turn 350.
In this regard, I am trying to play on the most difficult settings which permit victory with NTT and a self imposed rule of no fail golding.. So far it seems to be Lake,Huge, Low Sea Level, Perm alliances+no vassals+regular barbs on Marathon.
I assure you that an Immortal AI with 30 cities, techs faster, and fields a more lethal army, than a Deity AI on 10 cities.