Isnt the failure of Michelson -Morley Exp to Aether relative motion because the Aether WAS cause of motion?

Question

Were they not assuming a wrong Idea of what the aether really is?

Answer 1

No. The ether was proposed as a vehicle to support the wave motion of light, and under Newtonian mechanics, velocities add such that a reference frame of zero velocity could be determined. The failure of M&M to detect such velocity suggested that no such reference frame exists. The final nails were driven into the ether's coffin by two things: Maxwell's equations, which showed that no ether was needed to propagate electromagnetic radiation, and Einstein's special relativity, which gave a new mechanics that correctly described light's behavior without needing an ether to do so.

Answer 2

The first responder is exactly correct. I only want to add that in no way was their experiment a failure. Just because they did not obtain the results they expected, does not mean the experiment was a failure, it merely means they disproved their hypothesis. Given that it was a major turning point for modern physics, I would call their experiment a great success.