Two points.

1. Google fought then-giants such as AltaVista, Excite and Yahoo in the process of establishing itself as the leader in search space. The incumbents had economies of scale and (relatively) massive amounts of data to crunch through. Yet a Google happened!

2. ``Google's very existence makes it harder for similar services to exist." History has proved time and again that such a premise is false. When it does become false, it is usually because of `dissimilar' disruptions in the landscape.