The correct response is: The results of the Michelson-Morley experiment did not fit the theory of the luminiferous ether, so the theory had to be rejected.
The Michelson-Morley experiment was pivotal in disproving the existing notion of luminiferous ether as a medium for light propagation. Their failure to detect the ether led to significant changes in the understanding of light and ultimately contributed to the development of Albert Einstein's theory of relativity, which described light as a wave that does not require a medium.