"For the love of money is the root of all kinds of evils. It is through this craving that some have wandered away from the faith and pierced themselves with many pangs." (1 Timothy 6:10)
First and foremost the root cause behind greed is money as in the time of today it has become not less than oxygen. In order to make even just a simple living one needs money. However, some people have become too blind that they do unethical things to fill their bank balance.
"Do nothing from rivalry or conceit, but in humility count others more significant than yourselves. Let each of you look not only to his own interests, but also to the interests of others." (Philippians 2:3-4)