1. Guy shouldn't have been out of jail. He was free on the revolving door that's Milwaukee/SE Wisconsin's court system.
2. From the videos I've seen, he was honking (warning people to get out of the way?) at least part of the time. So it seems like the "fleeing another crime" (a stabbing) might be at least partly true, and not just an attempt at "controlling the narrative".
3. There's obviously a lot of speculation that it was a revenge attack for the nearby Rittenhouse verdict last Friday.
4. The perp supposedly has pro-BLM, anti-white, anti Rittenhouse postings, plus something about "How to run people down in the street and get away with it."
My gut feeling is that it's a combination of #2 and #3. Possibly fleeing and not initially intentionally targeting the parade, making bad decisions etc. but turned into #3 at the end either out of just not caring, or possibly just out of opportunity.