DEVJYOT GHOSHAL and UDITHA JAYASINGHE IN 2020, Mahinda Rajapaksa won elections to become Sri Lanka's prime minister, serving under his brother and president Gotabaya. In 2021, another sibling, Basil, was named finance minister, tightening the family's hold on power. Less than a year later, the country's pre-eminent political dynasty is in trouble, as protesters take to the streets making demands that would have been unthinkable before the economic crisis struck: that the president steps down. "Gota go home!" hundreds of people chanted along a leafy boulevard in Sri Lanka's commercial capital Colombo this week as cars drove past, honking their…