India’s large diaspora is tapping its wealth, growing political clout and expertise to help India combat a catastrophic coronavirus surge that has led to desperate pleas for oxygen and left people to die outside overwhelmed hospitals. Two humanitarian groups in the U.S. led by people of Indian descent raised more than $25 million in recent days to help India’s teetering health care system. In Britain, volunteers at three Hindu temples raised more than $830,000 last weekend by racking up miles on stationary bikes. The magnitude of the response reflects the deep pockets of many people in the overseas Indian community as well as their deep ties to India.