Given what we have seen happen at Supermicro, for example, CEO smuggling NVIDIA chips to China, it seems unlikely that no one at NVIDIA suspected a thing. Why wouldn't they want to bolster their China business?

An "exposure" of affair could very well be the best coverup: "couldn't control my dick" is the ultimate plausible deniability. Timing also makes sense. Better open an investigation and get it closed while this Congress is still in power, as the next one is going to be more in bed in LLM companies than hardware.