Because it’s just a rather large smudge on the window glass back-lit by a street light. It’s a great example of a low-light situation, and a low-resolution camera not knowing what to do with complex detail. The end result is a big blob of mostly one color.
If I had done this on purpose it would never have turned out quite so seemingly perfect.
That’s what makes it even spookier somehow.
He’s got a raging case of the pareidolias.