My fun answer for this one is that there is a future civilization facing collapse / extinction / "great filter" and they're (humans or AI) running infinite life simulations to try to determine what actions will give them the greatest probability of escape / survival. We're living in one of those simulated worlds. But that's very human / AI centric, and doesn't answer any of the same questions higher up. Maybe they know.
I have some fun thoughts around this problem which is maybe just as a lonely sculptor might sculpt a human-like figure that they can converse with to feel less alone (and from "one" make "two"), maybe a universal consciousness decided to create something & the illusion of "separatedness" (from one, many) in consciousness to feel less alone. Hence make a universe with lots of manifestations of consciousness to observe and interact with one another, and keep any true knowledge of itself a mystery to preserve the illusion.
But that's not a very scientific perspective, and all the questions above still remain.
Krang inputs 'teletubbies having tea with elon musk in the style of milo manara' and somewhere on deviantart someone makes it and the universe has a reason to be kept going.