Answer :
There are several reasons why monsoons were important to early indian civilizations, but in general they would flood the rivers, which was important for crop growth.
The early Indian civilizations, as all the other early civilizations, were heavily dependent on the big rivers.
The big rivers not just provided water for drinking and hygiene, but they were the ones that were enabling the large amounts of food production. The rivers were flooding their valleys each year, and with it they were leaving lot of fertile deposits in the valleys. Those deposits enabled the prospering of the agriculture, and also a very high production in it.
These floods were mostly created by the intense rainfall from the monsoons. The monsoons bring in so much precipitation, that even a small river will became relatively large one while they are present, yet alone a big one. Because of the effect that the monsoons had on the rivers on which the early civilizations very heavily dependent, the monsoons had a big place in the tradition and culture of these people.
