The company may be big, but their hardware orders are nothing compared to the orders for compute farms. They've gone on record recently about the Steam Machine saying there are some components they could not secure at all, for any price. Their service contacts are just not attractive when the world-ending AI farms are happy to pay more per unit and ordering more units total.

I do think they really should try their hardest to keep those replacement parts coming, but from the outside it's impossible to know how hard they actually tried. The only question is whether you give them the benefit of the doubt. You don't seem to, and that's fine (honestly I'm not sure I should give it either), but what I'm saying is there is doubt, the market is so fucked right now that this is actually believable.