probably because ishant has a bit more experience and a good defensive technique that the rest.
yashpal singh didn't let KKR down. Brendon Mccullum did.
mccullum hasn't done any of the jobs assigned to him this season well.
mccullum,i guess lacks communication skills with the players and is slightly shy.
get him out of captaincy and may be he can concentrate on his batting better.
gayle will be a good captain.
I don't know if you have noticed or not, but this is the worst team in the IPL. I mean look at the roster, except for McCullum, Gayle, and Ishant this team looks pretty poor. Then add in the fact Sharma is a poor 20/20 bowler, Ganguly is alright but he isn't playing that much cricket anymore. Once Gayle leaves they are in big trouble. But you can already see what's going to happen, KKR will come last and the owner will take the captaincy off McCullum and give it too Gayle. And during the "Off-Season" sign some big names, Martin Guptill maybe
I'm not trying to insult anyone here, and I'm not the biggest fan of the IPL since I live in NZ and all, so I'm no expert. But that is just my opinion.