Walmart have invested 16 Billion USD in Flipkart. It was the biggest deal for Walmart. Why they have chosen Flipkart? Because both the entities combine can create the synergy and benefit each other through various ways.
Walmart can transfer some departments in India with Flipkart like IT department.
Walmart can enter into E-commerce business with the help of Flipkart and in the same way Flipkart can enter into retail business with the help of Walmart.
There can be many more synergies arises by these two entities.
But the entity can become heartland only if there is the need of support like Flipkart need some entity which can help them to enter into Retail business and there should also be the ability with Walmart help Flipkart for what they want.