I don't think that follows, it is easy to imagine an alternative history without all the hissyfits about nuclear fission or with real investment into nuclear fusion starting in the 70s.

It's not just oil, it's also coal and other integral resources that are now difficult to extract because we are at the upper level of the S-curve and efficiency has dropped.

Well, coal is the resource that's gone, but all the metals - iron, silver, aluminum - aren't depleted (they don't disappear when we use them) and are much more accessible than they were before, because we dug them out from deep underground, refined them (especially for aluminum) and concentrated them in various places. If civilization would disappear, our scrapyards are better mining locations than anything the Romans had.

"What if something happens to all the books"

> Raytheon has called in retired engineers to teach its employees how to build the Stinger missiles heavily used by Ukraine’s military—using blueprints drawn up during the Carter administration.

https://www.defenseone.com/business/2023/06/raytheon-calls-r...

And of course, lots of resources have been depleted.