This is usually the norm with a node shrink. AMD had one, Nvidia didn't. The die size of the 5080 is 378, Navi 48 is 390 mm².
If something, AMD probably thought the 5080 would be the 5070ti instead (which would have been great), but was blindsided by Nvidia launching basically the same cards as last gen. So their 9070xt is now not a 5070ti competitor, but is close to the 5080.
I think this is the explanation that makes the most sense. I think they fucked themselves over by copying Nvidia's naming. If the rumors are true (and I think they are, we are in this situation).
RTX 5080 close in power to 9070XT
5070TI close in power to 9070
5070 close in power, probably to the 9060XT
5060ti close in power to 9060
Because of Nvidia selling us the same cards, they are now forced to price their products at a much lower price than before. I now understand what their problem is.