Life was not all strawberries and ice skating. A brutal, needless invasion had happened, and though he was hiding from his own kind, he never stopped planning how to stop them. He needed human collaboration, and so he contacted Walter Bishop.
Over many years of observing the historical development of the human race, he had come into contact with many humans, and for some reason he kept coming back to Walter Bishop. It wasn't until Walter Bishop showed up at his door wearing his expression of befuddled delight that he felt his own delight and realized he had a friend.