The theory of Special Relativity, formulated by Einstein in 1905, is based on the postulate that the laws of physics are the same regardless of the state of motion of the observer, so long as it is uniform. This is known as the Principle of Relativity, from which there follow many strange effects. While these behaviors seem paradoxical, they make perfectly good sense when seen as a result of the way fields behave, whether they be quantum fields or classical fields.
I call this the bottom-up approach. Although most physicists prefer to start with the Principle of Relativity, the bottom-up method provides insight into why these strange things happen. Even the Principle of Relativity follows from the bottom-up approach.
Either way, one must cope with a Rashomon reality in which observers in differently-moving systems see the same reality in different ways. Rashomon reality is very confusing, and is best left to the physicists to deal with.