No, the expansion was not “thought up to save relativity”. That’s not what I’m saying. The switch-over in terms occurred mainly in the 1990s, from “big bang” and “moving galaxies” to “expanding space” and “non-moving galaxies being carried along by expanding space”, and I say the switch-over in terms was designed to salvage and save the “c speed limit” of SR theory, AFTER the superluminal (faster than “c”) galaxies were discovered.

Look, if you run away from me at 5 mph, I can say you are “moving away from me at 5 mph”. Also, if you get in a car and the car drives you away from me at 5 mph, I can still say you are “moving away from me at 5 mph”. So, it doesn’t matter HOW the galaxies are “moving,” away from us at faster than “c”, they are still “moving away from us at faster than c”, whether “space is expanding” or not. But some cosmologists think this violates Einstein’s “speed limit of c”, so they don’t like it. They are afraid to “violate” anything Einstein said, even if what he said turned out to be wrong.

But, this might NOT violate the “speed limit of c” if the galaxies are not moving through any fields. The “speed limit” is actually based on Lorentz theory of the motion of atoms “through fields”, not the motion of atoms “through empty space”. So, “c” might still be a “speed limit” for atoms moving through fields, such as gravitational fields, but the distant galaxies might not be moving through fields.