General relativity was not produced in isolation, there were a number of other big names in mathematics and physics at the time trying to find a relativistic th

General relativity was not produced in isolation, there were a number of other big names in mathematics and physics at the time trying to find a relativistic theory of gravitation. Einstein will have been discussing with the other physicists and been familiar with their work. See for example https://en.m.wikipedia.org/wiki/Nordstr%C3%B6m%27s_theory_of_gravitation https://en.m.wikipedia.org/wiki/Nordstr%C3%B6m%27s_theory_of...