"there was a variation in the results"
Considering only the two facts of a) how long it took for mankind to come up with anything that could actually experimentally measure the speed of light at all and that b) the kind of equipment used to finally make that measurement was multiple orders of magnitude too imprecise to measure _variations_ in the speed of light which is why Michelson and Morley had to come up with something much, much more sensitive, it's not hard to imagine that the measurements they took had, you know, a non-zero precision error. The whole interferometer had to be floating on mercury to make the measurement at all, FFS!
"That discrepancy was confirmed later" [Citation needed] - also, clarification whether that was _the exact same_ discrepancy (now that would be something...) or just some discrepancy again, due to instruments inexplicably _still_ not measuring the speed of light with absolute precision (go figure...).