Why movies like Priyadarshan’s Kanchipuram?

I often wonder why some commercially successful directors try to prove themselves with movies that are similar to documentaries.

Take director Priyadarshan for example. He has made his name by making slapstick comedies, but now he has done a volte-face and made a film called ‘Kanchipuram’ a film about the plight of weavers in the temple town of Kanchipuram.

I can guess, without seeing the film, that it will be cry fest. It is not that depicting true to life stories is bad; it is just that I wonder why instead of making sensitive films like 'Veyil' or 'Paruthi Veeran' they go completely off tangent.