The mural that Francis Sinclair put together seems to have been inspired by Diego Rivera’s painting, Man, Controller of the Universe, which illustrates the aspects of contemporary social and scientific culture of the 1930s. But the similarities end there; both works depict different themes.
I'm not going to explain in full depth Diego Rivera's mural, this is not what my theory is about, but what I am going to clarify is the interesting similarities between the story of "Man, Controller of the Universe" and Francis Sinclair's mural.
Similarities:
Diego Rivera painted an unfinished "Man at the Crossroads" in 1933 for the 30 Rockefeller Plaza, in New York City. But he then ran into problems with John D. Rockefeller Jr. (politics). After that John D. Rockefeller Jr. ordered the mural to be removed/destroyed. Then in 1934, Diego Rivera repainted his original vision under the new name of "Man, Controller of the Universe" in Mexico City.
Francis Sinclair completed the mural in 1899/1907. When he went to Strawberry to reveal his discovery and theory, he was then dismissed by Church officials because they believed that his work could spread heretical beliefs into their community, similar to how John D. Rockefeller Jr. did not authorize Diego Rivera's painting because of his beliefs. The man depicted at the center of the mural bears some resemblance to Francis Sinclair. And the fact that there are 2 versions of RDR2's mural may also be a nod to Diego Rivera's original mural. Additionally, Francis Sinclair's hair color is supposed to be blond, not ginger, just like the man depicted in the painting, and both characters also share the same eye color (blue).
Shared Elements:
1. Machinery (Clock wheels).
2. Enormous figure at the center that divides the mural in half.
3. Atoms.
4. The cosmos.
5. Microcosm (Double helix).
6. War (Soldiers and plane).
7. New York City.
8. Technological advances
Conclusion:
Even though all of this seems to line up flawlessly, this is only a theory, not confirmed facts. I am currently working on a theory that explains why Francis Sinclair's design was changed to an Epsilon-themed one. And it is also tied to Isabeau Katherina Zinsmeister.