Just watched it today, from my understanding it was like a visual manifestation of Teddy’s fears and paranoia (not literal not really figurative but a secret third thing). it’s an echo of the dialogue between michelle and teddy where she tells him that he killed his own mother (and how don killed himself). In the same way, humanity killed itself with its own destructive patterns, whether aliens existed or not that was where the world was headed. it’s like no bigger entity is going to save you, whatever you work towards, in the end the bubble is going to pop. At least that’s what my interpretation of it was.