I made a video on IPv4 exhaustion with some interesting facts and take you are not expecting!
Made a video digging into why the internet ran out of IPv4 addresses, and the popular "shortsighted engineers" narrative doesn't hold up well once you check the math. In 1981, 4.3 billion addresses was almost one per human alive — for a research network of a few hundred machines. It wasn't a bad forecast, it was scaffolding for an experiment that never got its planned redesign.
The part I found more interesting: NAT was proposed in 1994 explicitly as a short-term bridge until real IPv6 migration happened. Thirty years later it's not a bridge, it's the permanent architecture — most of what's on your home network right now doesn't have a real internet address, it's sharing one through translation. IPv6 sits at maybe half of global traffic depending on the day, three decades after being finished, largely because NAT made the crisis survivable enough that migrating never became urgent.