The moat
Network effects in query data, brand as the verb, distribution via Android/Chrome, and scale in ads auctions. YouTube has its own creator network. Cloud switching costs are rising but still behind Azure and AWS.
Pain, risk, or retraining required to leave.
The product gets better as more people use it.
Patents, data, licenses, process knowledge, regulation.
Fixed costs spread over a volume rivals cannot match.
Structural ability to be the low-cost producer.
Pricing power from trust, habit, or identity.