I'd just say "market irrationality" and call it a day. TSMC is far closer to a monopoly than NVIDIA is, and they win no matter which fabless company is buying their capacity.
You could be right. But it could also be due to things like: automatic 401k injections into the market, easy retail investing, and general speculative attitudes.
If so, can you explain why Nvidia's market cap is much higher than TSMC's? (4.15 trillion versus 1.10 trillion)