Portland already had two vessels scheduled for Monday and Wednesday. I'm guessing Countess changed it's schedule around to deliver vehicles in Tacoma first, much like Glovis Chorus did — although I think it did that for the ice and cold.
We'll see, but I believe that it'll make it to Portland, just not as soon as you'd like.
As far as why it was anchored for so long…no clue. But a wild guess would be that the crew is allowed so many days off-ship every so often. Sam Francisco isn't a bad spot to chill.