This narrative is very unpersuasive, since the actual mechanics that are used to perform calculations in special relativity and the idea that they should apply to all matter were developed by Lorentz and Poincare starting in the 1890s. The moving clock idea was also introduced by them before Einstein in 1900 and 1904.

The most persuasive narrative to me for why Einstein is credited is because he moved to the USA at the right time and introduced these ideas to American scientists at the time when the USA was starting to become more scientifically prominent than Europe. Of course they would associate those ideas with Einstein and credit him, he would be the citation they would know about and wouldn't have any reason to cite further work since his citations are self contained enough for their purposes. It isn't nefarious, it isn't meritocratic: it is just pragmatic.

I don't buy that narrative. I think that Einstein's special relativity paper showed how the mathematics followed from first principles. Neither Lorentz nor Poincare did that. They may have had the mathematics that worked, they may have had it first. But Einstein told us why.

Which first principle exactly? Because they were already stating that the speed of light would be constant in all frames which is the only thing necessary to derive special relativity. Lorentz derived the transformations precisely to describe this fact!

Certainly not the lack of the aether; while it isn't necessary to describe relativity it isn't precluded either and cosmic time is a thing today. The spacetime we live in is a thing describable in its own right, on large scales it has a preferred time direction.

He was responsible for spreading those ideas, but he certainly wasn't the first one to express them. It is still respectful to give him credit for the spread of these ideas, but we don't need to pretend like Lorentz and Poincare were blind men fumbling around in the dark until he came along in order to justify our reverence.