If you took out the bits of relativity that were developed by others, you'd be left with not very much. Relativity without the Lorentz transform... I'm not even sure how one would resolve that. As I said, the vast majority of the insight was just taking what the math was already saying seriously. Einstein put it into a final form, and this is important and valid work, but it's not like he invented all the mathematical tools from scratch.
Either you've misinterpreted Adam Frank's work, or it isn't excellent.
I'll counter-cite Reflections on Relativity, which contains a lot of deep analysis of the mathematical history of relativity both before and after Einstein: https://mathpages.com/rr/rrtoc.htm which makes it quite clear both what he did, and did not do.
