The story actually gives the background of the holes. They were dug by humans. They aren’t supernatural and didn’t appear from nowhere, they emerged from older sediment layers that were raised back to the surface again after an earthquake. The story doesn’t specifically say it, but it implicitly builds on ideas the predominant religion in Japan - syncretic Buddhism - which is common for any literature and would be recognized readily in Japanese audiences. These people committed crimes and were punished in the past, and now they have been reborn again. Like all people they are ignorant to their past lives in normal situations, but their ‘souls’ are still bound to and resonate with the same infinitely continuous karmic system.
Great!
Oh, but I do see some questions here haha. I see your point, but to that end:
No, there really aren’t. All labor has is collective action (and although it seems crazy doctors are usually working class) . It’s the only way they’ve ever made progress, and where they lack it, workers’ rights are always eroded.
If healthcare never paid a decent wage in the first place, there wouldn’t be highly-skilled doctors and the population wouldn’t be at risk from suffering from a healthcare strike - because they would just be suffering day in and day out instead.