NVIDIA makes Tegra, they have their own ARM implementation in Project Denver, and they're exploring a RISC-V implementation (though they've made a custom RISC CPU named FALCON), so NVIDIA does indeed make SoCs and CPUs. They don't make modems, sure, but neither does most of the other ARM developers (the only that makes their own ARM CPU core and a modem is Qualcomm).
So it would definitely be in NVIDIA's interest to buy ARM. And I would have the same position as I do against NVIDIA if Apple, Samsung, Qualcomm, MediaTek, or any of ARM's other licensees wanted to buy them.