If the foundry business can create a competitive product that saves Nvidia/AMD manufacturing costs, they'll pay. Business allegiances change all the time when it impacts the bottom line.

If the Intel foundry business creates supply, even for people who are not Nvidia/AMD/Apple, they still win via increased competition on TSMC and Samsung.

Yes. I didn't say that this wouldn't happen. I just observed that none of the three players among AMD, Nvidia, and Intel have an active interest in working together. Practicality will trump, but I suspect that given a choice among Intel and another closely-priced, competitive foundry, both AMD and Nvidia will choose the latter.

> It is unlikely that Nvidia and AMD will want to use Intel as their foundry.

Why not? Nvidia seems to be very pragmatic in their foundry picks on what's available for example.

Couldn't you say the same about smartphone makers using Samsung's display panels, despite them being a direct competitor?

Unlike Intel, Samsung is first and foremost a component maker. Almost every phone makers use their commodified displays, batteries, memory/storage chips -- Samsung's phone division is just a side business.