Microsoft bought shares of Apple when it was on its knees. The foundry business doesn't compete with Nvidia.

Microsoft bought Apple shares for their own benefit instead of for supporting a competitor (it was too cheap for them and they could argue not a monpoly).

And solved some patent issues.

Of course it does. Do you think Nvidia likes being dependent on TSMC?

Intel's foundry business is unsuitable for NVIDIA to use to produce GPUs. Intel's foundry business is also not a complement in the economics sense, as in "commoditize your complement"; it's a substitute for TSMC fabs (but a bad substitute). The market impact of Intel's foundry business is that incremental improvements to the fabs used more or less exclusively for Intel's x86 CPUs does not lead to higher sales of NVIDIA GPUs. It would take an unrealistically huge advance in quality or drop in price for Intel's fabs and the output thereof to affect demand for NVIDIA GPUs.

Intel does so much more than CPUs, relatively speaking Nvidia is a one-trick pony.

Nvidia is slowly but surely getting into doing all those things.