Board Thread:General Discussion/@comment-35347861-20180419071457/@comment-9212235-20181211073222

You're REALLY close. We do actually know what happened to the Dwemer. The use of the Heart of Lorkhan and Kagrenac's tools, plus their psychic link known as the Calling, all contributed to them stacking their souls together (dubbed "soul stacking") and fused with Numidium to become its divinity.

The write up of the Final Report to Trebonius explains what happened to the Dwemer. While this was a fan submission, it explains in game sources written like an in world document. This has been confirmed by Michael Kirkbride (a developer of Morrowind) and references to it exist in other places such as in C0DA when Jubal says to Numidium, "You are the dissapearance of the dwarves," and from the Skyrim quest involving... I think Calcelmo? Shit, now I can't remember and my googling is failing me. Anyway, dude theorizes about the disappearance of the Dwemer and then he fuzes himself to a robut just like the Dwemer did.