It ended very quickly because they let it run its course. Highly contagious viruses like these burn through a population in no time if you let them. If you do what we do they stick around forever and you just prolong the misery.
Also, the severity of the outbreak that occurred in India is exagerrated. India has like fifty trillion people, so everything that happens there looks like an event of Biblical proportions. It also happened during the hottest month of the year when people are normally dying, and the lockdown that pushed many people close to starvation over the edge didn't help either.