ICC T20 World Cup:

Why India Lost To New Zealand In Must-Win Match
The Indian team hasn't had a decent break since their tour of Australia playing England home and away and the IPL before the T20 World Cup. The fatigue has finally caught up it seems.
No Playing Time Together
The last time the first team played a T20I together was in March when they played England. The lack of cohesion could have been addressed if the team had played more matches together before the World Cup.
No Fixed Playing XI
Kohli and Shastri have struggled fixing their batting line up with many batters playing in same positions in their IPL teams.
Struggling Bowlers
Despite playing the IPL in the UAE, India's bowlers have struggled at the World Cup unable to deal with the dew setting in later in the evening matches.
Misfiring Batters
Despite India's riches in batting, the batters have failed to get going with only Kohli and Pant scoring more than 30 runs in the two matches so far.