That's exactly what it is - exacerbated by the widespread use of public transit in those states.
When South Korea figured out that hand washing was a critical factor and implemented strict protocols (as in, people were not allowed to enter office buildings without washing their hands at a provided station outside), their case rate - which had been looking ominous - dropped like a stone.
Doubt it was that. Thery wore masks. Looking the super spreading events, none were surface-only. Some like the church choir were aerosol-only.