Special relativity was heavily motivated by a pile of puzzling evidence If you mean the Michelson–Morley experiment (apparent zero velocity of earth with respe

Special relativity was heavily motivated by a pile of puzzling evidence If you mean the Michelson–Morley experiment (apparent zero velocity of earth with respect to the ether), apparently Einstein himself claimed that wasn’t a motivation. I believe it was all about resolving the long-standing "action at a distance" question raised by Newtonian physics (Newton himself noted that this was philosophically disturbing but didn’t venture an answer). Intuition and philosophy, rather than experimental evidence and mathematics.