Yes he was! But Sir Fred Hoyle did not invent the making of carbon - he simply suggested in 1952 that since we are made largely of carbon and it is so abundant in the Universe, there must be some way it is produced. Also, William A. Fowler has not set the natural laws in carbon production that explain the fundamental astrophysics in the life cycle of massive stars. He simply figured out how the system can work.
We sometimes have tendency of attributing unconsciously great wonders of Nature to human geniuses who discovered explanations to them and forget this simple fact - not one hair have we humans made despite the fact that we may understand today a bit about the marvels of how hairs grow on our skin! ( toupees do not count)
The triple alpha process is highly dependent on carbon-12 and beryllium-8 having resonances with the same energy as helium-4, and before 1952 no such energy level was known.
Astrophysicist Fred Hoyle used the fact that carbon-12 is abundant in the universe as evidence for the existence of the carbon-12 resonance, in what is an example of the application of the Anthropic Principle: we are here, and we are made of carbon, so carbon must have originated somehow and the only physically conceivable way is through triple alpha processes that requires the existence of a resonance in a given very specific location in the spectra of carbon-12 nuclei.
Hoyle suggested the idea to nuclear physicist William (Willy) A. Fowler, who conceded that it was possible that this energy level had been missed in previous work. By 1952, Fowler had already discovered the beryllium-8 resonance, and Edwin Salpeter calculated the reaction rate taking this resonance into account. This helped to explain the rate of the process, but the rate calculated by Salpeter was still somewhat too low.
William A. Fowler (1911-1995)
A few years later, after an undertaking by his research group at the Kellogg Radiation Laboratory at the California Institute of Technology, Fowler discovered a carbon-12 resonance near 7.65 MeV, which has eliminated the final discrepancy between the nuclear theory and the theory of stellar evolution.