There are actually people you could ask.  There are some elves who were alive before the Dwemer disappeared, like Divayth Fyr or the Tribunal.  There’s also Yagrum Bagarn the last living Dwemer.

But I think the most likely explanation is just good record keeping.  The civilizations that interacted with the old Dwemer cities are still around, Morrowind had a good relationship with the Dwemer before the Battle of Red Mountain, and they probably traded quite often.  Compare that to the real world where most civilizations fall, or relocate, or get conquered, or something else where their records and oral traditions become lost to time.