Which would have saved a bunch of money from upkeep and accidents?

That’s highly debatable. Putting something in the ground instead of the air just adds a different set of factors eating away at the cables. Accidents happen underground as well as above. Excavators or farming equipment regularly cut cables buried in fields or at construction sites. The deeper you bury cables to avoid that the higher the cost gets. Also maintaining a network of buried cables has its own problems: Want to know where an overland power line was cut? Just look where the cable dropped. Want to know where a buried line broke? Start digging up the whole strand between the two transfer points.

Overall: Overland lines are cheaper and easier to maintain.