I believe we have yet to see kaido's character and what drives him.
I highly suspect that it has something to do with xebec.
Imo, he really respected and loved his captain, so much, that he even build his crew like him.
The only rule in kaido's crew is... strength.
If you are strong enough, you can climb up. Nothing more, nothing less. Put that together with whitebeards talk with oden, where he described his past crew (rocks) and it will make sense.
I don't buy the stuff with "he is sooo bored, so he wants to die/ start the greatest war ever".
Because that doesn't add up with his past 25 years. He steadily build up his territory, allances and crew. Just look at it, wano, samurais, joker/dressrosa, mass destruction weapons/ceasar clown, smiles/tobi roppo, etc. etc.
He said to oden "we were at a disadvantage at that time". That is not what someone who is bored and thus wants excitement would say. Because it is even better, when he has a disadvantage, since it would make the fighr even more exciting etc.
So no one can make me believe, that that what was shown and said till now, is true.
He has a plan and tries to execute this for at least 25 years. I bet it is the wish of xebec/what he tried to achieve or something like that. And we will see it.
AND kaido is NOT the strongest creature ever. AND he would not always win in a 1vs1. THAT is just the speculation about him what goes around the world. Meaning, it is the hype he receives from the FODDER of the world.
Everything else wouldn't make sense. His fight with oden, with big mom (they fought for 3 days, none of them were injured, so their power is NEARLY equal at least... like with ace vs jinbei or akainu vs aokiji) etc.
Not long till everything will be shown. I hope at that time, the fandom realizes the writing of oda (he hypes every fucking character up, the stronger the character, the greater the hype)
And btw, I am not saying that xebec is alive or so, I hope he is dead and stays dead.
So till now, we haven't seen kaido. Imo.