Einstein's breakthrough was far deeper, more philosophical than assumedThey did find relativity before Einstein. With all the formulas. In particular, what Einstein said about simultaneity and synchronization of clocks was straight from what Poincare said five years earlier.
Relativity is about general, qualitative principles, not about light or particular objects and gadgets
Some days ago, we had interesting discussions about the special theory of relativity, its main message, the way of thinking, the essence of Einstein's genius and his paradigm shift, and the good and bad ways how relativity is presented to the kids and others. ...
Did the physicists before Einstein spend their days by screaming that the simultaneity of events is absolute? They didn't. It was an assumption that they were making all the time. All of science totally depended on it. But it seemed to obvious that they didn't even articulate that they were making this assumption. When they were describing the switch to another inertial system, they needed to use the Galilean transformation and at that moment, it became clear that they were assuming something. But everyone instinctively thought that one shouldn't question such an assumption. No one has even had the idea to question it. And that's why they couldn't find relativity before Einstein.
Einstein has figured out that some of these assumptions were just wrong and he replaced them with "new scientific dogmas".
Motl repeats the widespread belief that Einstein found relativity by repudiating conventional wisdom and introducing new dogmas. That is not true at all. The most widely accepted theoy on the matter was Lorentz's 1895 theory. Lorentz had already received a Nobel prize for it in 1902.
Einstein's big dogmas were that the speed of light is constant and motion is relative. Einstein later admitted that he got the constant speed of light straight from Lorentz. He also got the relativity postulate from Lorentz, although it was Poincare who really emphasized it, so maybe he got it from Poincare.
Einstein did later argue against rival theories, such as Abraham's, but he never claimed that Lorentz or Poincare were wrong about their relativity theories. Other authors referred to the "Lorentz-Einstein theory", as if there were no diffence.xxc Even when Einstein was credited with saying something different from Lorentz, he insisted that his theory was the same as Lorentz's.
Einstein did sometimes pretend to have made conceptual advances in his formulation of special relativity, such as with the aether and local time. But what Einstein said on these matters was essentially the same as what Lorentz said many years earlier.
The formulation of special relativity that is accepted today is the geometric spacetime version presented by Poincare and Minkowki, not Einstein's. Poincare and Minkowski did explain how their view was different from Lorentz's.