Too bad it seems this clever Kaido doesn't apply anymore in current storyline.
Now he underestimated Luffy so much that after he defeated Luffy he put him in prison and the plan to break Luffy's spirit completely backfired. Luffy now got stronger after training advanced CoA with Grandpa Hyou, and also gained more allies (prisoners, Yakuza bosses and possibly Kidd's crew).
Kaido defeated Luffy only to put him into summer camp.
The one that's more concerned about rebellion right now is only Orochi but look at what he got. He got clowned by his subordinates behind his back, for believing ghost stories.
Now he underestimated Luffy so much that after he defeated Luffy he put him in prison and the plan to break Luffy's spirit completely backfired. Luffy now got stronger after training advanced CoA with Grandpa Hyou, and also gained more allies (prisoners, Yakuza bosses and possibly Kidd's crew).
Kaido defeated Luffy only to put him into summer camp.
The one that's more concerned about rebellion right now is only Orochi but look at what he got. He got clowned by his subordinates behind his back, for believing ghost stories.
Kaido not taking Luffy seriously is a myth. He just one-shotted him, put him in seastone chains and let Queen deal with him, since he wanted to make him a crewmember.
Why should he suspect anything going wrong there?
After all Kaido had Kidd imprisoned for weeks/months and nothing happened. In Kaido's eyes he just clapped one comparable dude and threw him right next to Kidd.