Accessing shale is trivial for our civilization, not necessarily for those of even 200 years ago.
- You have to know the shale gas is there
- You have to be able to extract, capture and refine it
- You have to be able to distribute it
The oil industry is filled with examples of people not "knowing" exactly what they were doing. Choosing to drill in a given location often included the possibility that there was actually no oil/gas to be had...that the well would end up being a "dry hole."