Two years after Oden’s return, Gecko Moria and his old crew fought Kaido and the Beasts Pirates in Ringo.
We saw tat the fight was a big deal event and that young Moria was actually kind menacing. Wich leave me to the question, how? How did Moria fought Kaido?
Think that Moria lost to a pre timeskip Luffy, yes, a peak pre timeskip Luffy, but still. Just for the sake of comparation, in the pre timeskip era, Luffy, Zoro and Sanji had to go all out, with the help of the other Straw Hats to take down a Pacifista. Two years later a Luffy without Gear 4 was able to KO a Pacifista of the same model.
So, how did Moria face against a Yonko? Even if we speculate that Kaido was not Yonko level yet, he was definitely a Yonko Commander level (btw, I think he was already Yonko level for sure), something like that was more than enough to defeat with easy someone of pre time-skip Luffy level.
So there are two options.
1-The first one, I’m gonna be honest, is the more likely. This option assumes that the “fight” was actually like the confrontation between Kizaru and the Supernovas. Not really a fight but someone unilaterally wiping the floor with other people. Maybe Kaido was bored, decided he himself was gonna take care of Moria and his crew. He played with them from sometime (killing) and then seeing Moria broken, he simply let him go.
2-The other option is the one that involves a little bit of theory about Haki. In this option Moria was actually a lot stronger than he was when we met him.
He had a powerful Haki and was someone that could have actually forced someone like Kaido to make an effort. But then what happened? Well we know that Haki, in all of its 3 forms, is actually a physical manifestation of Will. We also know that someone with a broken will becomes useless, and that can happen with even someone like Luffy.
After Ace’s death, Luffy became completely useless, and was not because of his injuries, but his mind. Seeing his brother dying shattered his will. Luffy began to doubt his abilities and started to think about how he could possibly become the Pirate King if he was too weak.
After that, Luffy had a little verbal and physical struggle against Jinbe who told him not to regret his brother’s death, and that he had not lost everything yet. Luffy then remembered that he still had something priceless: his crew.
But what if Luffy had lost even his crew? What if someone’s will is broken beyond repair? Moria had all of his Nakama killed in front of him (and he probably did care a lot for them), maybe after that he simply didn’t have the will to summon his Haki anymore and became a shadow of his former self.