India’s largest conglomerate is reeling from the shock resignation of its chairman, who leaves a vacuum just as the coffee-to-cars group executes a massive reinvestment program over the next five years. Natarajan Chandrasekaran’s decision to step down in February jeopardizes Tata Sons Pvt.’s $120 billion wager on future growth and brings an abrupt end to nearly a decade of leadership that helped push India into more advanced technologies. Some of the conglomerate’s current and planned projects could slow down, be scaled back or stretch out longer as it awaits new leadership, said people familiar with the matter who asked not to be identified as the details aren’t public