I'd guess that magic has something to do with their ridiculous rate of advancement. Especially in the case of the Dwemer, those machines are unbelievable... The gods actively loving with the mortals probably has something to do with it, too. I wouldn't be surprised if a good bit of the technology they have came from enlightenment from the gods.
It's safe to assume they didn't reach their level of technology in 2400 years. Humans have had a long period of time, far longer than recorded history, where they lived in tribes until they founded the first cities and started recording history.