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 brain dead does a person have to be to see an entire parade in front of them and think, “this can’t be some organized event, I must just be able to drive right through here!” Main character syndrome. Or more likely, a sociopath just looking to murder someone.
Here’s an idea. Find another fucking route. They plan these events, publish the routes in advance, have a police presence there, and place them in areas where they won’t cut off people’s only means of getting somewhere.
Do you ever find yourself in this situation? Here’s how to handle it without being a fucking moron:
Pull off the road.
Pull out your phone.
Google “<your city>” critical mass route <today’s date.>"
Is that really that hard? Or are you someone who is so concrete sequential that you have one and only one route you can drive, and any other route home will break your mind? What if a sink hole opened up on the road you normally take home. Would you just blindly drive right into it because you this is the route you take home, and damn it if you’re going to let anything stop you?
You have a very poor understanding of how these critical masses work, they do NOT function like normal protests, at least in the US.
Most critical masses of cyclists are intentionally made to be spontaneous, barely organized, and they do not give prior warning to locals (through the local media or such), the government, or even the police. The whole point of the intentional disorganization to escape the authorities when they eventually come in to restore order. The reason why they’re called “critical masses” to begin with is because large turnouts is the only requirements of these events. There is no organization or leaders or hierarchy or anything to hold accountable.
So what happens is unsuspecting locals going on about their day get met with a mob of cyclists who are blocking traffic, ignoring any and all established safety laws, and disrupting the flow of the city. The people who do come across them don’t know where they came from, where they’re headed, or what they’re going to do next.
That’s why you can’t “go around them” like you’re suggesting. You’re basically trapped in your car until they go away. These events put the cyclists in danger and they put the drivers in danger. That’s why they’re considered dangerous. If they functioned like how you imagined they functioned, then way less people would have an issue with them.
https://en.wikipedia.org/wiki/Critical_Mass_(cycling)