Because they're not building single family homes in Medina? Multi family housing in various parts of the metro (including Snohomish county). The Seattle Times has more information including a bit more about geography:

https://www.seattletimes.com/seattle-news/homeless/microsoft...

The key is zoning and it sounds like they have some local buy-in from politicians (see the attached statement of mayors in that article). I'm skeptical that happens, NIMBYs have a way of stalling up zoning, but it's a still a step in the right direction.