Shivika Sabharwal’s nerves kicked in the second she spotted the size of the crowd. It was mid-September, and Sabharwal was standing center stage inside a massive event space at Mumbai’s extravagant Jio World Convention Centre. The space, which had recently hosted the star-studded wedding between billionaire heirs Anant Ambani and Radhika Merchant, had been transformed into a sea of green — green spotlights, green archways, a neon-green light display — in honor of WhatsApp’s first business summit...