Prolog was one of hot A.I. prospects of the 1980s. It could be a way to build an expert system. Japanese fifth generation computers were supposed to,run it fast.

Then A.I. boom fizzled. Neither the first or last business cycle.

However, there's still work being done adjacent to 5G using real prolog, by people who thought it was an interesting idea: https://github.com/bitlaw-jp/the-constitution-of-japan

Prolog is still used in the development of expert systems, though when those systems are shipped, they have often been rewritten in an imperative language based on a Prolog prototype.

The fifth generation project, from what I understand, died because of a dedication to custom hardware using already-obsolete fabrication tech -- mid-70s flipflops-on-IC tech over late-70s microprocessor-on-IC tech, wire wrap, etc. There was an inability or unwillingness to iterate on original committee designs. By the time it folded in 1998, everything involved looked like stone knives and bearskins. Those boxes wouldn't have been able to run it fast by 1980 standards.