He's probably at that point in his possum life that he just doesn't care anymore what the cats, dogs in the other yard, other possums, and even the skunk have to say about him.
I mean its to get all worked up about and play dead over.
The big one seems to have left of its own accord but I guess it was a she instead of a he. I saw a little possum in my yard a couple of days ago and caught it using a strawberry for bait last night. I hope that's the last one but my garden has lots of possum hidey holes so I'll have to wait and see. I turned the one I caught loose in a river bottom where it should have good pickings.