The Strain is a love story as it was promised in the very first episode. It stays very true to the origin of vampire stories, while Guillermo only twists the supernatural horror, not it's romantic essence. In The Strain's case Girl won the Boy and they lived happily ever after. They could have taken it on another direction, and let the series be an example of how the horrors can rule at the end of the day.
In a twisted way the Master was fighting a game of survival, and for a long time he was the only one. Everyone else and their dogs were against him. Nobody understood him or wanted anything to do with him. Least with his vision of world domination.
Who would want humanity gone and the world living in the perpetual darkness? Us as individuals might never see it but for a hive mind, humanity's win might not be the thing they would expect to see. At the end I like the Strain. It was a good series, with mind boggling concept that gave us a good look into a real possibility that we might face in some other world in the future.
Who knows if in some weird planet we encounter hive minded parasites dominating the whole egosphere?
Well done Guillermo, The Strain crew and the Fox.