Last July, at a SoftBank conference in Tokyo, CEO Masayoshi Son brought on stage Vijay Shekhar Sharma, the founder of Indian startup Paytm. Son described Paytm as the “uncontested No. 1” payment service in India. SoftBank had invested $1.4 billion in the startup, helping to fuel India’s mobile payment boom a few years ago. 

But by the time Son singled out Sharma for praise, Paytm had already begun to lose its tight grip on India’s $65 billion mobile payments market. Over the past two years, rival Google’s payment service grew rapidly in the country after the Indian government launched an open-source payment system that made it easier for the U.S. giant to compete in the market. In December, the number of Paytm users who made at least one payment during the month declined to less than 40 million, from about 45 million a year earlier, according to people with knowledge of the figures.