Washington only has a population of 7.7 million, so it wouldn't make sense to have as many universties as California, which has a population of 39 million. For its size though, Seattle is one of the best educated places in the US...
I think the poor startup ecosystem has more to do with a lack of VC funding, and most people working for big companies like Amazon... and Amazon being notorious for suing to enforce non-competes, which are legal in Washington.
https://www.ftc.gov/news-events/news/press-releases/2024/04/...
[0]: https://www.reuters.com/legal/us-ban-worker-noncompete-agree...
Western (WWU) in Bellingham is decently sized (~14k). There are some smaller schools in Seattle itself like SU (~4k) and SPU (~2.5k). And there are UW's branch campuses in Bothell and Tacoma (~5k undergrads apiece).
Outside of the I-5 corridor, Central (CWU) and Eastern (EWU) both have ~11k undergrads.
We have UBC, SFU, and even UVic closer by, and the punch a bit higher in computer science. But these days many of the UW professors that started companies back in the late 90s/early 00s are long gone.
An investor once said to me "If you can't figure out how to get office space for your startup, you shouldn't be an entrepreneur"...unless you need specialized lab space for your biotech startup or similar, I kind of agree....