I think some of you are overthinking it. Grynewaht was something of a recurring comic relief figure - a bumbling brute who showed up multiple times before meeting a grisly end. This is hardly something new for the franchise, let alone the genre. If the protagonists are going to be encased in plot armour then it's only fair that the antagonists, too, get to enjoy that selfsame luxury from time to time. Either temporarily or permanently.