We use "con" here because a road is considered as an animated object in Vietnamese ^_^ (correct me if I'm wrong haha)
It's true. The road goes on and on, as if it has a life of its own. Also, "Con" is somewhat more intimate and dear because "đường" also plays a significant role throughout our lives.
Perhaps because it looks like a worm :)
why is it not "Con đường đến SỰ thành công"?
It's also correct.
Đến can be used as a verb and therefore I said: the road leads to success, but was rejected.