Why Bilbo?

[Celuien]

Originally Posted by The Hobbit, XIX

"Then the old prophecies have turned out to be true, after a fashion!" said Bilbo.

"Of course!" said Gandalf. "And why should they not prove true? Surely you don't disbelieve the prophecies, because you had a part in bringing them about yourself? You don't really suppose, do you, that all your adventures and escapes were managed by mere luck, just for your sole benefit? You are a very fine person, Mr. Baggins, and I am very fond of you, but you are only quite a little fellow in a wide world after all!"

The conversation does imply participation by Providence in Bilbo's adventures. Gandalf is telling Bilbo that the course of his journey was intended to run as it did, at least with respect ro fulfilling the prophecies related to Smaug's demise. That would lend support to the idea of Bilbo's being chosen for the adventure in some way beyond Gandalf's inital understanding being present from the beginning, although, perhaps like Gandalf, Tolkien wasn't completely aware of it until later.