Why is the universe quantum in nature? The answer is to make the universe casual and to save time in terms of its formation and progression.
If you look at the emission spectra of the hydrogen atom, it displays very specific photons implicit of very exact energy levels. These energy levels are quantized, meaning they are very specific, with gaps or dead spots between them. The probability is 1.0 or 0.0. This is not random but casual.
It is this exact quantum nature of the energy quanta of hydrogen, that allows us to infer the universe from billions of light years away. If these energy levels were random, we could not conclude anything. All that we infer is based on the exact nature of the quantized and exact spectra for the various atoms.
Since the energy quanta of the hydrogen atom are very exact, and are limited in number, with gaps between, the result is the universe is able to progress faster, thereby saving time. In other words, if event A had to happen before event B could occur, since quantum limits the options for A, this will speed the occurrence of Step A, compared to having a universe with unlimited random options for A. In the random universe, we would need to cycle through all the random options, like a deck of cards, before B could occur. But with quanta being limited and specific, there are only a few options for A, so B is ready to happen quickly; saves time.
The saving of time means we can use time for other things, beyond just maintaining space-time. For example, acceleration, which is the directing affect of force on matter, has the dimensions of d/t/t; distance divided by time, divided by time. Acceleration is two parts time and one part distance. Acceleration adds extra time to space-time. The forces of nature makes use of the extra time, saved by the quantum universe. Force saves us even more time, and makes thing even more causal, compared to random.
Random is not consistent with the nature of a quantum universe. Random is really an artifact of observation that uses using energy, instead of matter. The hydrogen atom is matter. This tiny piece of matter defines exact energy quanta. Once these energy quanta are released, the game changes, since the energy is subject to change, such as via Doppler or red shift.
When these quanta leave matter; hydrogen, they are always very specific and exact. However, since motion is relative, and there are things moving at all types of relative speeds, the energy quantum, once released can appear to change and be all over the board, in terms of final energy observations. This changing nature of the energy, used for observation, is what makes the universe seems more random. Physics has projected its own observational choice and limitations, onto the universe, instead of see the universe as it is; quantum, casual, and time saving.