Ok. Here's this Huge, Almighty Dragon who almost everyone is afraid of that destroys towns within minutes and defeats some of the world greatest heros....and he gets killed by an arrow her could probably pick his teeth with?
There are several thing that are included in the cause of Smaug's death.

-The black arrow of death that had never failed Bard
-Smaug'a weakspot
-Bard's good arrow skills
-The placement of the weakspot...it's near the heart, isn't it?
-etc.

Hmm...I don't know how to ask this question...

Do you think luck played a part (again) in the death of Smaug? ....or..Anything else that could have caused him to die(+ the arrow)? ..Or was it just "his time"?