The weather in Portland might have been nice, but the weather at the airport might have been foggy. I've seen many times (especially airports near water, i.e. Columbia River, etc.) where the runway was shrouded in fog, and the terminal buildings and the entire rest of the planet were in the clear.......you still can't land in those conditions if the visibility is below the legal minimums.

The dispatchers at NW are a very competent group of specialists....your lives are in their hands every single flight you take. I can almost guarantee there was a very valid reason for not selecting PDX as the divert. Not real obvious to outside observers, but apparent to all the players who had all the info.....(As an example, it's possible PDX might have had some runway construction or repair underway, shortening the usable runway length by 3,000 feet. The aircraft that diverted might have had an inop thrust reverser, or inop brake pad, which requires a runway of x,000 feet. To most of us: the weather was fine, the runway was open, and the aircraft healthy. But to those with all the info, there is a very valid reason for that airport not being a valid alternate.)

This crew:

Complied with the weather/landing criteria established by the FAA.

Complied with customs requlations established by Customs and Immigration.

Complied with crew rest requirements established by the FAA.

Although it's uncomfortable for all involved and the press it gets sucks, those who comply with the rules tend to live to fly another day.......