We know that a hot soup of plasma as it cools (as space expands) can produce light elements if the baryon-photon ratio is just right and the space expands quickly enough so that the neutrons and protons fall out of equilibrium - a theory advocated by Ralph Alpher. We also know that Deuterium and Helium can be produced by fusion of hydrogen atoms in stars, a theory advocated by Fred Hoyle. The internet is full of articles that tell us that BBN is one of the pillars of Cosmology, but I can't find a single one that says why it's favored over Stellar Nucleosynthesis.
Please explain the reason/evidence for preferring BBN over Stellar nucleosynthesis for the production of light elements.
