Physics is super old but for most of that time we didn't have the intellectual tools to do physics well. Once maths, engineering and the scientific method devel

Physics is super old but for most of that time we didn't have the intellectual tools to do physics well. Once maths, engineering and the scientific method developed enough, the experiments were relatively easy to do (as the OP pointed out, Rutherford was able to do his experiments on his own) and the key results followed.