Many cities in the US have built their transit systems around their highway networks because all they need to buy are vehicles, and they can quickly have reasonably competitive transit services up and running for cheap.
This brings us to West Seattle. West Seattle has numerous buses that go downtown; they all go along the West Seattle Bridge, up Highway 99, and then into downtown Seattle towards the 3rd Ave bus jam.
However, the Alaska Way viaduct no longer exists, so the only express part of the ride is now the West Seattle bridge, which is clogged until the exit to WA-99. Without the Viaduct, the bus stops being as fast as it used to be, increasing demand for driving.
If you are dependent on buses and highways for transit, the issue is that when you have a major corridor for transit using highways, you need to replace it in a way that does not punish transit riders.
If you simply remove a bus highway and do not replace it with rail, you will end up with worse transit. Worse transit will lead to a higher car modal share, which puts more pressure on politicians to increase parking, reduce density, and make all infrastructure more expensive. When demolishing a highway carrying mass transit, you need to replace it with a rail that is better than bus lanes. Otherwise, you might make your transit less urbanist.
This is why the West Seattle Link is a good project. Even light rail carries more people than buses and for a lower cost per passenger kilometer.
You can either have a car-dependent city or a rail-dependent city.