All we know, stars have the greatest mass in the universe, and about 90% of the mass of stars are hydrogen. In the fusion reactions of stars, hydrogen is converted to helium that produces light and energy of stars. Then it is enough to add a neutron and a proton to the helium nucleus to create heavier elements nuclei.
On the other hand an electron and a proton are needed to produce a neutron in the fusion reaction.
Based on the principle of having the highest symmetry and equilibrium in the nucleus, we probe the shape of the nuclei of the elements that could explain all possible isotopes.