The universe began with what then led to the 25 elementaries (and possibly more as discovered in the future) of the Standard Model, each of the entities of a type being identical to one another, and each elementary entity having to be of a specific unit energy level called a quantum.
In another thread, the “what led to them” is explained by quantum fields, but that is of little concern here, but for that there was energy in the beginning, too, and that there was simplicity at the beginning also.
From this conglomeration of stuff became all the higher wonders of complexity that we see about us now.
Nothing more was added in between the start of the universe and now. The recipe is ever as it was at the beginning.
Thus all that happened and became in between the beginning and now has to be purely physical from the base ingredients of the elementaries, as forming atoms to stars to molecules to cells to life to brains to consciousness and whatnot.
That shows in a nutshell that the going-ons in the universe had to have been purely physical.
The Transcendental Temptation
The desire to find purpose and meaning in a scientifically explained universe that otherwise seems "soulless" is likely the very human factor motivating spiritual seekers. People mistakenly assume that a purely naturalistic physical universe is devoid of purpose, meaning, and morality, and that only a universe infused with supernatural or paranormal magic can supply these qualities.
"The imagination draws a fanciful picture of a transcendental reality, some kind of celestial kingdom. Time and again the theistic myth appeals to the hungry soul; it feeds the creative imagination and soothes the pain of living. There must be something beyond this actual world, which we cannot see, hear, feel, or touch. There must be a deeper world, which the intellect ponders and the emotions crave. Here is the opening for the transcendental impulse. Yes, says the imagination, these things are possible.
— Paul Kurtz, The Transcendental Temptation: A critique of Religion and the Paranormal