Every single Nvidia launch is like this (except the 40 series if I remember correctly, you could basically just buy those), I think it’s a deliberate choice to have short term shortages. Apple chooses to stockpile devices before putting them on sale. Just two different ways of selling products, there’s no conspiracy just plain old supply management.
Apple’s logistics chain is configured for massive stockpiles of inventory. It’s unlikely GPUs have the same setup. In order for there to be no shortages of a GPU at launch you would need to have sufficient inventory to fully absorb the day one rush in every region. How many GPUs would that take?
If Nvidia shifted all 40 series wafers over to 50 series the 5080 should have decent supply soon. If not then it was clearly an intentional decision to use that capacity elsewhere.