It's a severe engineering challenge to hide massive heat exchangers on the scale of the datacenters built in the industrial area near Dulles (coordinate example: 38.9817915,-77.417775). Find those on a map and observe the scale of their cooling and generator systems and then try to find anything comparable that's been built underground.
Just wanted to make the point you don’t have to pay to excavate the cave :)
edit: 61.9340107, 5.5084207 are the coordinates
https://new.abb.com/news/detail/5924/abb-solutions-power-eur...
There are mines with plenty of space in them, and heat removal can be done with water cooling. But who is going to pay 50% more for that when it isn't needed 99.99% of the time?
Huh? The ones I know of have plenty of connectivity. The real issue is your first, that people prefer to just put their stuff in two countries over paying premium for having their servers under ground.