[Eomer of the Rohirrim]

But no matter how events turn out, there will always be a chain of events leading up, and we can look back along the chain and see all manner of ways in which the future could have turned out differently.

The Lord of the Rings happened the way it did because of that small event way back in the chain, but there could have been an even mightier tale had Thorin and Gandalf not met!