User blog comment:Edrea/Why so many bad things happened because of Merlin?/@comment-4495575-20130619065059/@comment-5674726-20130624215604

Maybe Merlin feared that Uther might recover fully, but still, there's only hope as long as people are alive.

I'd say that it's more a case that Merlin no longer believed Uther to be necessary. In the early seasons, he protected him less because it was the right thing to do and more because he believed that Arthur wasn't ready to be King. After Uther spent a year or so as a broken man, with Arthur ruling the kingdom, I'd say that Merlin no longer felt the need to keep him alive. He deemed Arthur to be ready to be King and therefore felt that it was neither necessary nor desirable to prolong Uther's life. At best, he was keeping Arthur from becoming King in name - which Merlin mistakenly believed would bring about a golden age - and, at worst, there was a slim chance that he might recover and be able to retake the throne, which Merlin would have seen as a major setback to the wonderful reign he envisaged for Arthur.