Your mistake starts with thinking Whitebeard was ever stronger than Kaido. He never was.
Every version of Gaban is weaker than Kaido.
Kaido is known for his one-on-one strength. We saw both the Gorosei and the CP0 agent reiterate that. In the end, it all comes down to Kaido versus his opponent.
Anyone who comes to Wano ends up facing Kaido one-on-one. Big Mom was literally freed so she could fight Kaido herself, and Kaido was the one who asked for it. Oden vs. Kaido, Luffy vs. Kaido. No one under Kaido’s command is allowed to interfere.
Green Bull sees commanders as weak trash and even says they cannot afford to lose to someone like him. That makes it clear the commanders were never the reason he stayed away from Wano. In the end, the real obstacle was Kaido.
Luffy not only needed a gazillion allies to take down Kaido’s army, he also needed Tama to use her abilities on Kaido’s men to turn them into allies. Oden danced naked in the streets because he didn’t think he could defeat Kaido and Orochi’s army, yet we know for a fact Oden was stronger than pre-prime Kaido. Kaido’s strength in 1v1 was never the sole factor.
What do you think would have happened if Luffy had beaten Kaido but his whole crew along with his allies had been decimated by Kaido’s army? You think he’d have defeated them on his own? Lol.
Lol at WB being weaker than Kaido. WB was Roger’s equal, Kaido was never on their level. Maybe he was stronger than the sick version of WB that showed up at Marineford, but that’s about it. Kaido still thought highly of Oden’s strength 20 years after their fight and had PTSD, even though he was way below Roger and WB.
WB, Roger, Rocks, Garp and possibly Shanks are in a tier of their own, above the likes of Kaido and BM. Their portrayal made that very clear.