nice video, fairly close to the reality. i have only minor quibbles. yes, he got it right, the early universe was like a dense fog of electrons and protons (after having expanded and cooled to that stage from a stage of interacting quarks), quite hot so that light only traveled a short distance before interacting with another free electron. but over time the electrons became bound in their ground state to protons, and matter became transparent (Hydrogen is a clear gas, relatively transparent to visible light photons). so he showed that when we look outwards, we see a portion of our universe receding from us as that opaque wall, so far away that we 'see' it via super-red-shifted photons in the microwave region, giving a 2,700K blackbody spectrum with a z of about 1071.
after the first stars formed, nuclear fusion could commence in earnest after they went supernova, showering the early galaxies with high-Z elements. astronomers refer to the 'metallicity' of a star to determine if it is 1st, 2nd, 3rd generation due to enrichment with high-Z elements (which are usually Iron/Nickel, or other metals).