More could always be said, but I posted a similar question around a year ago :

The Indian subcontinent was the birthplace of Buddhism. The teaching of Buddha found lots of success in foreign lands such as China, Myanmar, and Indochina. Yet in its homeland, it is currently a very small minority. How could this be?

/u/iitii wrote an answer to my question here, while /u/JimeDorje linked to an answer they posted on an older thread

Like mentioned, this can always be expanded on, however I provided a brief answer to a similar question question earlier this week, and at the end of my comment I also listed several excellent responses from other users on previous questions of this nature. In the same thread, u/JimeDorje and u/GoblinRightsNow also provided some great further details to the question.