Getting minor injuries from Kizaru's light sword, which is one of his higher-end techniques and Luffy's apparently weak to slashes according to Zbois, and all that without using advanced haki to block with lol.
Kizaru ran away because he realized he couldn't beat Luffy, just like Lucci changing target to Sentomaru because he needed the Seraphim on side to have any chance.
Why do you call them "mere clones", for all we know they're not that much weaker than the real Kizaru and there were multiple of them.