Kolaveri Di- A non-planned song that turned out into hit

You might be thinking that Kolaveri di which broke all records and become hit all hove the worls with more than 1crore views in few weeks of launch would had been a planned creation.
But Nooo.. This song was just an instantaneous creation,, with Dhanush son-in-law of Rajnikant singing just for chill... Directions for song were given by Dhanush's wife Aishwarya and composer Anirudh who is just 21yr old
Why This Kolaveri Di (Tamil: வொய் திஸ் கொலவெறி டி, Voy Tis Kolaveṟi Ṭi ?; English: Why This Murderous Rage, Girl? Ladki puchti hai ki itna katilana gusa kyun
What ever may be the story Kolaveri Di is adefinite hit with "good music"
So Why this kolaveri kolaveri Di