So I think luck, usually in the form of timing, is the main differentiator for growing huge. However, there are several points to make here. Luck is certainly not enough, and most of those companies who reached massive scale had:
1. A strong product that solved a huge market problem.
2. The ability to listen to the market and maneuver accordingly.
3. Great ability to execute - build stuff fast enough and at a sufficient level of quality.
4. A technological solution that is far from trivial, especially at scale.
The list above is what I thought before Eric’s question. But Mr Schmidt added another, fifth point: 5. An inherent property of the service that pushes it to scale.