The idea fills me with dread. NVIDIA isn't new to anti-competitive practices, and having control of ARM would make it easy for it to compete unfairly in the market.
ARM is everywhere. AMD CPUs have an ARM Platform Security Processor. AMD is working with Samsung on integrating RDNA into mobile chips, and NVIDIA could derail that. In fact, it could derail any deals that don't involve NVIDIA GPUs (or ARM Mali). It could even potentially force Apple to use NVIDIA GPUs in ARM Macs.
I hope that if NVIDIA does attempt to buy ARM, that governments will see the potential problems and stop the deal.