Gekko Moria vs Kaido

[SSJ2]

So I'm reading through Thriller Bark right now and Gekko Moriah claims that he would have beaten if he had his current crew + Oars. Is he completely delusional or did Oda change how powerful Kaido was?

 

[Captain Cadaver]

It's most likely a bit of both. There's no real justification for Moriah's rationale, making it apparent this is yet another part of the power creep Oda didn't plan out in advance. The assumption Kaido was far weaker in the past doesn't work either when Chapter/Episode 0 shows Moriah fought him after Roger's death at which point Kaido was more or less as strong as he is currently.
Perhaps Moriah was banking on using his crew to distract Kaido and steal his shadow, but even that's a big stretch when it'd require getting past his subordinates.

 

[SSJ2]

Maybe he knew Perona could beat Kaido singlehandedly