That's a point I didn't actually think about, touché. Let's go through this then:

Before Covid (in my country at least), there was this massive push for more homes, because the interest rates were so low. Everyone was building a house, because it was so very cheap (in interest at least, not necessarily in costs). At that point, wise developers might have decided to not take on any big new projects, focusing on finishing their current ones instead of trying to ride out this bubble.

Then Covid hit and the supply chains broke down. That was sudden and couldn't be expected, I'll give you that. But now, four years later, the main reason (in my opinion) for the low occupancy is the newfound interest for WFH, also resulting from Covid. Who needs an expensive condo in a crowded city if you can have a cheap flat in a small town instead?

So in this case, I'll (partially) retract my prior opinion and instead state that while a crash could've been seen somewhere on the horizon, Covid with all its consequences certainly couldn't have been foreseen.

I'm not familiar with the housing prices in Toronto compared to smaller cities in Canada, but perhaps those developers need to bite the bullet and lower their asking prices, because I'd imagine selling for less is still better than holding onto dead weight, praying for demand to go up again.