The north part of West Seattle also basically has the one bridge. And WA did have an I-5 bridge collapse a few years back, although IIRC it was collision-induced structural damage:
I live in West Seattle, and there are technically two - there's also a drawbridge for pedestrians/cyclists/two lanes of traffic. Both are pretty new, and work well; the Magnolia situation, on the other hand, is a lot tougher. The residents of Magnolia are also known to really fear additional connectivity (especially public transit) in part due to an unfounded fear of crime.
https://www.thestranger.com/slog/2018/07/02/28583329/magnoli... (title sarcastic)