there were other reasons for the new route. The old leg was on a BNSF freight track. BNSF track, BNSF freight trains have priority of the Amtrak Cascade train. One section of the old run is between Nisqually Reach (a body of water)and a series of cliffs. Rocks, sometimes very large would fall on the tracks. This had been a maintenance problem for years. The new route, no freight trains, no rocks and it saves time.
Over a hundred mil spent to save about 10 to 15 minutes. IF the trip is on time. That’s not a wise use of public money. It’s a boondoggle.
AFAIK, passenger trains still have priority over freight trains.