It's the maximum speed of causality, not the speed at which all things are caused. The speed limit of causality. If the rest of the theory of relativity was correct but there wasn't a maximum speed, then it would be possible for an effect to precede the cause. Relativity got rid of absolute simultaneity but some things still need to happen in a certain order. I think when people say "speed of causality" the "maximum" bit is implied.