In the 1970s it was also popular to fear grave resource shortages here on Earth. Turning to space was an easy low-imagination solution when you weren’t seriously considering the logistics of how to make it happen. It’s more a manifestation of the fears of the day than anything else.

This shortages haven’t really materialized. If anything we have far too much oil, not too little, and can keep on burning it for a long long time (and suffering consequences). Minerals for your car batteries? We can have lots by just seabed-mining right next to some sensitive ecosystems. Etc, etc.