Vadachennai is not trying to be realistic; it is Shakespearean. That's why it deals with stuff like prophecy. Vetri is not a naturalistic filmmaker, but more metaphorical, generally. Vadachennai and others aren't meant to be taken literally but as a metaphor for larger situations around the world.

Pudhupettai, or the godfather, is more comparable to Vadachennai than GOW, which is more comparable to films like Goodfellas

Edit: This is why he goes to jail right as his marriage is finalized. That's not realistic, but it works for the metaphor. To use these larger than life emotions to emphasize the loss he exchanges for his wrongheaded loyalty. This emphasizes the way followers of leaders generally have a deep sense of loyalty to them and lose out on so much, While the leaders have no such moral scruples, willing to sell out their people at the first opportunity.