This was a Critical Mass event, which is why the bicyclists are taking up all of the street as a way to reclaim the streets and protest the lack of safety for riders under usual conditions. It’s not legal, but protests are never useful if they’re fully legal now, are they.
How would a person who has no idea that it is called a critical mass event know to google when a critical mass event is held?
Is it really that hard to understand not everyone know what this is?