Well, there was a large crowd of people firmly ensconsed on the front lawn of Parliament, some calling for the outright overthrow of the Federal government, with no effective police control.
There was definitely enough people to try to storm Parliament, even with a portion of them involved.
May not have been a significant risk, but low probability/high impact things can/do happen, so discounting that possibility completely is naive.
It's fundamentally a judgement call, which the people with the authority to do it made. If people don't like it they can express their discontent with their votes.
Fundamentally seems to be that the City lost the plot early, had no real plan to get it back, and doesn't seem to have made any actual plan. I'd be curious to see how many officers were actually required to clear the streets, but I think it was a lot less then 1800 additional cops.
Maybe not a lot less. I counted 20 different public order units, give or take one or two. That’s not far off a thousand right there, maybe more. Then there were numerous tactical teams for overwatch, a lot of uniforms to take custody of and process prisoners passed back by the public order units, a lot of uniforms (day shift and night shift) to hold and secure the ground we had taken back, lots of members on outer cordon to stop or control traffic into the area generally, a bunch in various logistical roles, lots of extra uniforms as a protective presence at various federal sites in Ottawa… I don’t have a number to put to this, but 1800 isn’t out of the ballpark. And there were still normal non-convoy related policing requirements on top of all that. It was a lot. I’ve never seen anything like it.