I'm a Catholic from Kerala, and you believe me - as far as i know, (where i live anyway) there are farrrrrrrr more many kerala christians than goans. There are a lot of goan christians, but there's way more in number. We as a community, are very active in church. But like everyone else, most people come to church on Sunday. In my family, we are very religious, which i particularly enjoy, we try to go to church every day. I only know three catholic goans (children), while i know a couple hundred keralites (children) and much more adults - obviously since i'm apart of that community. The faith our parents received from their parents carried on towards us. Back in India, we are a very religious folk. Celebrating all the catholic feasts as a vibrant community brings us together.
Back in 50 CE, Jesus' apostle - Saint Thomas came to kerala - thats where our ancestors converted to the Christian faith, I think we were mostly hindus before that.
My mum said that we came from India, as in the 2000's there was a huge lack of nurses and health staff, so the NHS recruited A LOT of people from India, a lot from Kerala too. So I'm guessing quite a lot of keralites came back then.
I know many keralites, and the lack of kerala hindus and muslims is that they don't migrate here that much. There are a lot of Kerala Christians, Muslims and Hindues in the Gulf, Austrailia and America as well.
Of course, I could be wrong about the number of goans, since i'm not one myself - i don't know much in detail. Just a keralites' point of view.
:-)