And again we find ourselves here.
It doesn't matter "why" a universe exists. UNIVERSES ARE PURE TEXT. THEY HAVE NO CONTEXT! As such, they are best treated as math treats identities: they are the product of all operations that produce the result.
Just asking "why is there a universe" is not a sane question, any more than "what single operation is 5?"
There are a lot of operations that evaluate to 5, and I assume an equally infinite number of operations result in "universe".
Our universe can be a deterministic simulation, best we can tell. Until such a time as something exposes the text inside to context from outside, the context will not matter. And even then, for those of us inside, the event will only be pure text still: it will be only indicative of the extent of information that event transmits.
As an example, using a video game: if I spin up a copy of Super Mario Brothers, hit start at exactly 5 frames in, jump once exactly 2 frames in, get hit by the goomba, and then five frames later save the state, and then repeat this process on a different emulator across the world, I have played the same game. I can compare their binaries and they will contain the same data. If I am mario, I cannot say that the buttons even exist. I only know that I am signaled five frames in to jump. I don't know who spun up a game or that this is even a game. I know (things started happening), (signal at five frames).