Regarding the three Techeuns and Uldren...

Going back to the Taken War, we find Mara Sov's armada go toe to toe with Oryx's fleet. We all know the result of that: Oryx wins the battle, but sacrifices much of his fleet with his Dreadnaught's superweapon. Fast forward to the Dreaming City, we find Sedia, Shuro Chi, and Kalli, Taken and being controlled by Riven, who was being controlled by Savathûn through Quria.

And rewinding a bit, it would seem that Uldren was undergoing a sort of Taken sickness.

So, my question is, how were they Taken in the first place? Last I checked, Oryx's superweapon destroyed the Awoken armada, heavily damaging Uldren's ship to where it crash lands on Mars (in one of the Lost Sectors). As for the Techeuns, it would've seemed like they died with Mara Sov.