I don't think there's a big conspiracy here.
I think what's happened is a combination of factors:
1) Shipping guns and ammo has liabilities that other products don't. If Canada Post leaves a $1500 iPad on your front step that was signature required and it gets stolen, their liability is the replacement cost of the item. If UPS leaves 1000rds of 9mm on your front step or a gun and it gets stolen, then they have a massive problem.
2) Whether it makes sense or not, shipping companies eliminated or severely curtailed signature verification due to COVID-19. Everything gets left on the front step, lobby, etc.
3) Guns and ammo are a small portion of their business but are essentially in a class of their own as controlled goods that come with extra liabilities. With the pandemic, if the choice is to basically put guns and ammo in their own category requiring signatures or stopping the shipment of guns and ammo, the loss is small enough to make the latter decision.
4) Companies may just decide that it's not worth their effort to do it anymore, especially if their company is garbage and mistakes have consequences. Canpar is Exhibit A here.