The City has always had an undercurrent of left wing extremists and/or radical labor unionism. There is still a statue of Lenin in Fremont (long story).
However, these people call themselves "Anarchists," and have become a real problem for the past decade. It was on local TV much of the night. Every local news outlet was following them. But SPD did a marvelous job herding them down to Sodo (area where the stadiums are and no small businesses). It petered out after that. Couple of officers hurt and some protestors.
Seattle has been very permissive with these kinds of folks for too long. Finally, they got tough. Panhandling, and other issues are big problems inside the City. I live south of there and the culture is very different. Going to Seattle is like visiting another country. But the City is much more diverse now in terms of locals vs transplants. The transplants are more corporate and won't put up these weirdoes anymore. Even one of our long time news anchors, Steve Raible (former Seahawk and now play by play guy as well), openly criticizes the marches.
You're right on another thing - Who is funding these people? We were discussing that last night.
I doubt they have jobs. What do they do the rest of the year? Plan for anarchy? Isn't that an anachronism? What kinds of meetings are they?