I've been thinking about this since I re-read the lore for the Dwemer, but my theory is that the Dwemer DID attain Divinity, but their bodies were unable to maintain a physical form. Through that, they were banished to a place where they could have a form, Oblivion. In Oblivion, their physique morphed into the lesser Daedra, depending on which realm they had been sent to. We are able to conjure them because our mortality is able to break the shackles on their binding to Oblivion, rather, it switches those binds onto us. My evidence for them being Daedra is based on the fact that Daedra also favor stonework and that they also harbor a resentment to having something superior to them. This also explains why Daedra can never truly be killed, because their Divinity will not allow it, forcing them to be banished.