What made Ganguly keep Dhoni in the team after the initial failure of Dhoni?
Sourav Ganguly came across MS Dhoni while playing the Challenger trophy in 2004 and was impressed with his big hitting in the net. Dhoni scored a hundred hitting Ashish Nehra out of Wankhede Stadium. He was selected in the Indian team soon and made his debut in December 2004.
At that time Ganguly wanted another big-hitter in the team to help the trio of Sachin Tendulkar, Virender Sehwag and himself. Ganguly thought that MS Dhoni could be the match-winner he was looking for.
Ganguly had a tremendous habit to give many young budding players an opportunity to perform and Dhoni was one of them. Ganguly was known for backing his players when they needed him the most. For example, Virender Sehwag used to bat as a middle-order batsman for India. It was Ganguly, who promoted him and gave him the opportunity to open the innings for the team and later he went on to become the most successful opener India ever had after Sunil Gavaskar.
Ganguly always believed one or two matches cannot define a player. For a player to perform you have to give him a fair bit of chances to express himself. The list includes Balaji, Gautam Gambhir, Yuvraj Singh, MS Dhoni, Irfan Pathan, Zaheer Khan, Dinesh Karthik and several others. These players have gone on to become champions of the game. Had it not been for Sourav Ganguly, these players might not have become the legends that they are today.
Dhoni failed in his first four matches scoring 0, 12, 7* and 3. Then Ganguly decided to give Dhoni a chance at No.3 for 3-4 matches. Ganguly left his spot of No.3 in the next match Dhoni was sent up the order to No 3 against Pakistan in Visakhapatnam and proceeds to smash 148 off 123 balls and since then there was no looking back for him.
Ganguly always believed in giving chance to youngsters and he even gave up his batting positions to fit in a player. So it was not only for Dhoni but it was Ganguly specialty to back up players and give them enough chances to showcase their skills.
Source - Quora