Kaido even had a weaker crew back then
Just stop making excuses
Kaido crew wasn't strong even now it isn't even that impressive
WB knew he cant beat Young or prime kaido less than extreme diff.
Says you, no one in their right minds would say Kaido has a weak crew, the only basis you say that is by comparing his crew with BM's, whose Luffy with half his crew manage to defeat....Yes, he didnt beat her ass, but his crew managed to steal the poneglyphs, rescue their teammate, fuck up BM's territory, and beat 2 out of 3 of her strongest commanders. That IS a fucking defeat no matter how you look at it.
Its not that information can easily get out of Wano, by the time he found out anything happened with Oden, he was already long dead, same with his wife, and likely their children since they where missing. Even soo it was just a matter of giving the Ok for them to go to Wano, wich he was probably preparing to do...Then the whole BB thing might have happened, with them waiting for Ace to deal with BB before going to Wano.
As for marineford...well, saving a nakama>>>>avenging a nakama.