The movie was a masterpiece for those able to read between the lines. The ending was perfect for anyone who understands the trauma developed need for dissociation that has become a symptom of the world that we currently reside in. I'm ashamed to say I was shocked to find that this film was review bombed by people who don't even seem to understand it and how they are inadvertently playing into the theme of this movie. Step 1: Sever our connection to each other, Step 2: Confuse us with Terror and misleading information, Step 3: We do the work for them.
I'm gonna be honest about he deer because I didn't understand them until the credits rolled, but pondering it further the answer was simple: An animal which is normally known for moving in small families if not solitarily were choosing to create a wider community as a necessity for their survival.