They’re already investing in renewables. However, solar is still quite expensive compared to coal (EDIT: NVM, it’s not, especially in India, I can only assume that the main driver for coal is the absence of capital costs for increased consumption as well as the intermittency issues)
Wind doesn’t have the short lifespan issue of solar, and is therefore cheaper, however intermittency is still a problem and storage solutions are hardly feasible (nevermind cost-competitive) at those scales.