For one religion to grow at the expense of another, the new religion must fill some need the other fails to do. This is happening in real time in the country of Nepal.
I think a lot of the world’s history can be summed up as, “I have a better deal for you.” Obama defeated his opponent with this after eight years of Republicans. Trump defeated Clinton after eight years of Democrats.
If we go back 2,000 plus years, Christians told people under Roman rule they had a better deal. Today, Christians are telling the untouchables in India they can have a better deal. They offer health care to people who have little.
What people who are on the winning side of these struggles often forget is the the clock keeps ticking. The time comes when yet another group or way of thinking will push aside what is new and better today.
In the U.S. today, the majority of young people are not interested in following the Christian faith. While the future is not completely predictable, it seems like this demographic group has heard the call that someone or something else offers them a better deal and they are switching sides.
If history offers a glimpse into the future, the untouchables will be Christian for a long time and then will move onto something else. The same is true for China and Africa.
Persuading people to change religions is about offering a better deal. It never ends.