I thought that was strange too, but my head canon now is that the King healed him, like he was able heal Galadrial. That's kind of a weak excuse on my part, but I don't care.😃
I like his character, so I am glad he survived.
With Sauron, the impression that I had was that he was only able to control those that had given their minds to his deceptions, which many of the Elves of Eregion had.
Anyway, just my .02