> Didn't the overbuild of fiber directly lead to Google buying up dark fiber, and then lighting it up later

Yes, but the lag there is decade-long, and a bunch of heavily fibre-invested companies went bust before anyone saw the upside.

In the same vein, it's very possible that early movers-and-shakers in the LLM space will overextend and end up bankrupt before LLMs find a long-term profitable niche