There are multiple reasons for the postponement. Some states in India already announced that theatres would be operating at only 50% capacity in next few weeks. Delhi even closed down the theatres completely few days ago.  In coming days, few more states are expected to impose restrictions on movie theatres occupancy.   Another major reason is that RRR is mainly a Telugu movie (not a Bollywood movie) and it's biggest market in India comes from 2 Southern States where Telugu is the main