Board Thread:Skyrim/@comment-1157147-20130322022136/@comment-91.125.21.177-20170908192838

I think the Dwemer found his or her remains and brought it to Blackreach for studies, then Alduin summoned the dragons back to life and the reason he/she can't fly during combat for is because it can't multi-task.

This theory supports how it got down there, why it got down there and why it doesn't fly during combat.