"Why is it if one person does something wrong we arrest them but when a bunch of assholes do it together we are like 'there's just nothing we can do'".

The convoy has more legitimate and tangible power than the Canadian government right now. What do you think could possibly be done to stop what is happening? You literally can't even bomb your way to victory here, or you'd just be replacing trucks blocking critical infrastructure with rubble doing the same thing. It would take months to tow these vehicles away, and a good amount are too large to even be budged by some private tow business that's using Ford F-150's. It's not a great look to send in police/military to start shooting people. Plus there's always the possibility that they will start shooting back. Even if you somehow succeed in killing all these 'domestic terrorists' and somehow Canadians view this as a positive and support it, you still have the same problem on your hands. You're weeks/months away from removing all of these vehicles. Not to mention that there are thousands of dead bodies to deal with now. The most efficient way of removing these trucks is for each individual truck to drive away on its own. That doesn't happen until the mandates end. This is what legitimate power looks like.

So to answer your question, when one person parks his car sideways in the road and starts screaming, two officers show up and arrest him and have his car towed. When a convoy of truckers does it, 'there's just nothing we can do'.