Consider: Intel traded NVIDIA a P4 FSB license for access to NVIDIA patents back in 2004. Begin Intel nForce era. What did Intel get? Posit: Intel implemented the NVIDIA patents in their CPUs and Intel now doesn't wish to stop using that patented technology or they'd have to revise the Centrino/Core Duo platform..
It's pretty safe to assume that Intel didn't want GPU-specific patents, since they haven't developed a miraculous high end GPU peerage, and their integrated GPUs are plodding along as ever. Intel wouldn't want something like NVIDIA networking or chipsets; Networking and chipsets are commodity products, not bargaining chips for a P4 FSB license that would eat into Intel's motherboard market share. The only thing left is Occam's Razor slicing patents into the Intel CPU. Intel can't afford to stop using CoreDuo, and return to P4, so Intel needed to placate NVIDIA into continuing licensing patents that are critical for the Intel CPU.