I think it was about how quickly and decisively they moved to secure supplies, how competently they negotiated the contracts and how effective they were at organising vaccination programmes. I think ultimately it was decisiveness that made the biggest difference, while other countries dithered about which vaccines to support.

Now arguably this exposed e.g. the UK to using a vaccine with unfortunate rare side effects (I was vaccinated with AZ myself), but on the other hand this has shielded us from a third wave of infections and probably saved tens of thousands of lives.