Why are Walmart's Waltons nearly 5x richer than Reliance's Ambanis?

Walmart owners Walton family is nearly 5x richer than Reliance Group owners Ambani family, as per Bloomberg data. One of the primary reasons for this is Waltons' scale, generating $681 billion annually and serving 270 million customers/week. With over 10,750 Walmart stores worldwide, Waltons have global consumer exposure while Ambanis' diversified oil-to-chemicals empire is largely India-centric.