Researchers found several sings that indicates indus River valley civilization was influenced by religions such as Hinduism, Buddhism and Jainism.
These religion consist of several teachings on what to do and what not to do, which later on developed into a set of moral standard that form the culture in that civilization (such as the development of caste system, worshipping multiple Gods, etc)
The development of caste system, no matter how bad it is, also contribute to the economy by the creation of job specialization among the people (some is assigned for farming, some for trades, etc) which contribute to the increase in economy.
But since many of the wars during that period happen because of religion, many groups within that civilziation that held different religions started to fight each other and lead to the decline
