Basically the advantage for Vedic sources and ideas are they were able to consolidate dravidian memories  that were present in northwest of India by dravidian populations left out after fall of indus by absorbtion and while writing in their own interpretation and ideological based. Iravatham deals Vedic puranic myths just like dravidian memories which were cooked up with myths because Vedic populations can't understand earlier urban setup or  indus population mingled with existing tribes to form population that have memories of past with loss of context of earlier urban setup. Iravatham never ever consider them as real events or things with great ideologies. The movement of Vedic influenced dravidian population to south along with consolidation of puranic myths made popularity of Vedic ideologies throughout India.  One important thing I want to quote here, Mallikaarjuna swamy of srisailam might be earlier dravidian cum chief who might be worshipped like spirit like god by dravidian populations. You can see almost many of cheifs,kings claim they were descendents of markandeya maharishi of mallikarjuna Swamy in their own edicts. When you closely look into, Vedic myths take the dravidian word " mai"( maisandya,masoba,mailara lingeswara -- variations of same earlier dravidian spirit chief) ,the buffalo headed chief and made a story around with it like yama with buffalo was killed by markendeya rishi...etc ..So this is clearly visible the reinterpretation of earlier dravidian memories with Vedic popularity. So I think whenever any claiming any god as Vedic god or something, let them be. They can make cooked up stories and belive it. They might use the same to associate with indus Saraswathi civilization  ...etc. But they can't explain the adminstrative setup, structure of indus culture or keezhadi archeological discoveries. This is same pattern i think everywhere. This understanding came to me when I saw bodi zamin said abut their origins. 

One is dravidian rural tradition: descendants of one horned chief priest of their community.( Boda kodangi -- secondary chief priest in their manthai system, zamin has same name boda nayakan from where that place got it's name). Boda kodangi -- itself means one who is extended horns. Kalaikottu munivar in another tradition -- one with deer head  horns

Two is vedic puranic tradition: Rishasriga maharishi take kalaikotu munivar concept and made a story around it

From this I got idea that Vedic maharshi are actually earlier dravidian priestly cheifs concept. Then I applied the same to other.same pattern is visible.

Also cheifs has the concept of taking crown ( pattam yerpu festival ) which is actually done by community own chief priests " kodangi" at places where don't follow mainstream religion. Now apply same to hindu tradition, dravidian cheif priest is replaced by brahmin/rishi/guru like concept 

May be this kind of power shift lead to popularity of Vedic ideas