ICE is trying to incite a riot in order to justify having the army flatten Portland
Or to justify bringing more military for law enforcement to normalize that and allow the president to declare martial law for political reasons. This is playing with fire. It's hard to imagine a future president worse than Trump, but it's possible, and citizens, local police, and possibly National Guard or military units could resist them militarily, and then we're at civil war, which would be nightmare for everyone.
I think that's actually a lot. It's around 4.5% of voters. Just under half of voters voted from Trump, although some of them may have changed their minds since the election. There are some people who aren't into demonstrating on the streets. There is always some percentage of people with something else going on. For example, my teenagers didn't go because they had both run grueling races yesterday morning. My wife and I were at risk of being late because we went to a neighboring city yesterday morning to watch our kids race and because the roads and bus system were overwhelmed with people going to the demonstration and to the Badgers game, but when we arrived thousands of people were still pouring onto East Wash (the main road the Square).
That was just our life. I'm sure someone else's kid had a big race or performance that did conflict, or their parent just received a bad medical diagnosis, or they had to work, or they're in the middle of moving house. 4.5% of voters getting out and marching is a lot.