The reason is simple, as simple as a sentence or two. Nature is the best teacher of mankind, and there are many vivid and simple examples.

Everything in the universe is strange, but without exception, it is made up of or produced by protons, neutrons and electrons. The appearance of the universe is complex, but the essence is simple. Perhaps after the further development of science, it is not surprising to find that protons, neutrons and electrons are all made up of an X atom.

The sun is the mother of life on the earth, and everything on the earth grows in the sunshine. But the composition of the sun is very simple, mainly composed of hydrogen atoms.