why they started the new trend to release songs in many langauges

for pan Indian films they do it

Song click kar jati hai toh uss region mein thoda better business hota hai.

Most of the AR Rahman songs are made that way and so does that of other stars who are really popular like Salman, sridevi

eg:- main pyar kiya, guru, chandni, Dil se and lot more

It's just they have started promoting them now along side the Hindi version.