Though there are uncountable reason but some of the them can be considered as disastrous. If we carry out separate match analysis than every player will be blamed, but as a whole these are some consequence -
Pitch related problems: The Indians played a predominantly spin oriented attack even at Barbados whereas the West Indian pitches seem to have regained their pace and bounce. Other teams like Australia and England banked heavily on their pace attacks and succeeded.
Short-pitch ball: The Indian team were unable to handle shot-pitch stuff from the quickies. India capitulated against fast bouncy deliveries and lost key wickets. They did not realise that with only two bouncers per over permitted they should have waited for length balls to hit.
Strategic issues: By not practising together as a team between matches since 'the players were tired' and by not sending an advance party of the coach and players who were free from the last stage of the IPL they had little time to acclimatise.
Selection errors: Those who saw Robin Uthappa, Virat Kohli and S Badrinath bat during the IPL, would wonder why they were not picked for Team India. Uthappa in particular has the ability to take on pacy short pitched bowling and score at a rapid pace while doing so. With Sachin Tendulkar and Virender Sehwag not in the team, India needed Uthappa to bat up the order in the West Indies.
Waning form: Unfortunately for the team, two of its main batsmen, Gautam Gambhir and Yuvraj Singh were woefully out of form. Yuvraj was unlucky to see one or two good hits go straight to the fielders on the boundary, but Gambhir looked totally out-of-sorts. Coupled with the disastrous performances of Murali Vijay and Yusuf Pathan, this meant that India's batting firepower was greatly diminished.
Praveen's injury: Praveen Kumar bowled impressively in the only two matches that India won. His injury left the team without a genuine swing bowler who could make crucial early breakthroughs.
The IPL effect: MS Dhoni had the guts and the plain-speaking-ability to state the facts as they stood at the post match conference after the loss to Sri Lanka. He blamed the IPL, not for the amount of cricket played, but for the post-match parties and the excessive travelling involved in the 45 day extravaganza, that left the players jaded and stale.
The J factor: Ravindra Jadeja may be one of the most talented all-rounders in the country but he has been found wanting in the last two World Cups. Sent in at number three at Lords last year, he lost his team precious time by scoring at less than a run a ball. In the Caribbean he was woefully short on confidence and was hit for several sixes.
Zaheer below par: India's pace spearhead Zaheer Khan bowled well below his penetrative best and cost India extra runs. He went for over 40 runs in most matches. Ashish Nehra was more effective in the death overs but ploughed a lone furrow.
Dhoni's absence: He seems to be absent in the field all the time, his decision making ability was not upto mark, his focus and control was not matching the pace of international cricket, which became the main reason of the exit.