The Chinese had invented printing presses with movable type before (but just didn't have that much use for it, given their writing system). Lorentz and others had worked on precursors to special relativity, relativity was in the air. If Einstein hadn't been there, we might have had to wait a few years more for some lesser minds to come up with a piece of relativity and his contributions to quantum mechanics each, but we would have gotten those achievements in any case.