Well, what functions could the universe serve? It is not a toaster or a hatrack or a lawnmower or something else with an obvious function.
Some hypotheses which present themselves:
(1) It's an experiment to find out what a universe with such-and-such laws of nature would do. Granted someone with the ability to make universes, it is not implausible that they'd have the desire ---
we would, if we could.
(2) It's an ornament. Clearly the universe is stunningly beautiful, and beautiful things without an obvious function are generally ornamental.
(3) It's a form of reality TV. We sapient beings do such amusing things, like burning one another alive or invading Russia in the winter. Properly edited, it would make fascinating viewing. After all, people watch the History Channel, don't they? What if someone wanted to watch history?