Over confidence and not to count the opponent.
~Edited~
We see this behavior from time to time in Virat Captaincy, even in International matches. some time Virat the Batsman overpowers the Captain Virat. In International matches, Dhoni and in some extent Rohit keeps him in Check but that's not the case in IPL.
When a team wins then this overconfidence thingy hides behind the winning moment or we called this aggressive captaincy etc but when team loss then it looks very ugly.