To take the reverse perspective, why it is coming up now, I think that in the 80s and 90s, the increase in processing power came in the form of faster processor

To take the reverse perspective, why it is coming up now, I think that in the 80s and 90s, the increase in processing power came in the form of faster processors. Then, pretty suddenly, really, over the past decade, that trend hit a wall, and instead we're getting more cores, but at the same speed. This rekindled the interest in concurrent programming, and Lisps have a distinctive edge in that space.