I wonder why dark fiber was so cheap in the early 2000s when google famously started using it to link their datacenters?

Not to mention that a huge percentage of the fiber laid in the 90s was never used. It was put in the wrong place or turned out to be the wrong type or was just lost when the "the internet is the future and will change everything. it runs over fiber and we'll need so much more than we could ever lay" companies went bust.