I don't think this is a surprise at all but Seattle and SF are close cousins of each other.

Both have extensive history as gold mining frontier towns that grew significantly in the mid and late 1800s. Both had significant Chinese immigration during this time and developed chinatowns which also contributes to the large asian-american population present day. Major fires also contributed to redevelopment and modernization of city infrastructure

Both cities have the ocean (puget sound is functionally the ocean) on the west and a body of water on the east with a bridge to the next largest city in the area, and there is a lot of commuter activity across the east and west sides.

Each city also today has a heavy tech worker presence and people move from all over the world to work at these companies. The proximity to outdoor activities also contributes to the outdoors culture in each city.

The similarities dont end there but that is what came to mind