Are you implying hinduism is much recent to kerala?
In my information, kerala before 500 AD was a sort of dravidian place where people had no organised religion, but they worshipped their ancestors and a warrior goddess. Women drank and quarrelled. In short we can say a "Thora" (coastal) culture akin to vizhinjam, chaavakkad, mattancheri meenchantha existed them.
Into this first comes vedic aryan influences. Then arrives buddhism and jainism. Then comes judaism and later christianity and islam.
The gods and demo gods like ganapati, durga etc are comparatively recent imports. Doesnt mean wht the dravidian believed in wasnt hinduism. (though not in modern keralite form).
We can say similarly abt roman catholicism. Compare the roman church of 900 AD with that of 2001 AD. You will not believe they were the one and same organisation.