There's another reason why PDX went away - longer-ranged equipment and liberalized air agreements with other countries made it possible to bypass the hitherto-obligatory need to stop on the West Coast before proceeding to many Asian destinations. As a result, PDX would have had to rely extensively on connecting traffic, which (a) Delta was not providing effectively and (b) has far lower yield and profit margins than O&D traffic. In short, the PDX Asian hub was doomed one way or another, and DL likely benefitted in the end from dismantling it "sooner" and minimizing the financial damage vs. holding on until the aftermath of 9/11.