I don't think this is entirely accurate! It's true that Darius's chariots lost to Alexander's phalanges at Arbela, but that's not because Persia was especially unsuitable to chariot battles. Where Persia was unusual was in continuing to use chariots 600 years after everyone else had moved to spear formations! Alexander and Darius III weren't born until centuries into the Iron Age—in the usual chronology, after the Iron Age and in Classical Antiquity. So, if there's a terrain factor in play here, it must have been that the Persian Empire must have been unusually well suited for chariots!

It's true that there's debate about to what extent Mycenaean Greece used battle chariots in the Bronze Age, when chariots dominated the battlefield throughout Egypt and Asia Minor, and I didn't know that. We don't have the extensive written record there that we have from China, Hatti, Egypt, and the like, but we do have archaeological finds. https://en.wikipedia.org/wiki/Military_of_Mycenaean_Greece#C... claims that they were used to some extent, but https://www.ancientworldmagazine.com/videos/mycenaean-chario... says that in northern Greece they weren't used at all!

However, contrary to what I was saying above, it turns out that there's ample evidence of chariot use for battlefield transport—like a tiny armored personnel carrier rather than a tank—from at least Mycenaean Greece until the Celts got genocided by Caesar.

Thanks for the information!