How Jason1's world got created?

Jason2's world was not a spin-off from Jason1's world. It's parallel. Jason1's world was not source.

The box is just a way to pass between worlds (which is impossible, but hey it's fantasy-scifi).

Every decision made by every conscious being, human or otherwise from the big bang on, or even interactions with variability between inanimate objects, splinters off a divergent universe. I don't find that the science supports the Hugh Everett Many Worlds interpretation of quantum uncertainty, entanglement, etc., and it's my view after years of studying the matter, that science in general has gone off the rails and needs to get reigned back into a scientific method and mindset. But it sure makes for some interesting storytelling.

If you liked this and enjoy this kind of trippy multi-timeline type story, you might want to check out Triangle (2009) or Predestination (2014). Or perhaps Primer (2004) or Time Lapse (2014). Or even the Tom Cruise blockbuster Edge Of Tomorrow (2014).
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Never believe or disbelieve. Always question. Rebuke bias, a.k.a. groupthink, a.k.a. ideology, the bane of skeptical, logical reason.

I like to think of it this way. Jason2 is the main character and Jason1 was initially nonexistent until the box was made. Great show, I really hope there is a season 2.