Theory: Jax is the creator of the digital circus and/or the first human. Originally it was probably just void. He made Caine, the world, and the other NPCs to stop his friends from abstracting, but it doesn't work. He has seen every single person abstract and that is why he's closed off, abusive, and emotionally distant. That's why he never goes to funerals. That's why he can break the fourth wall. That's why the first two pushes were of them. That's why he was the last to get an episode with pomni. He is the antagonist.

I bet That's why we never see what happens when He holds his breath. That's why Caine glitches when Jax is mentally unstable