I wrote "chatbots" in gwbasic based on my reading of programming books, inspired by programs like eliza and text adventure games from the late 80s. Later I ported the code to more advanced basic dialects, and linked it to a tcp stack and connected it to things like irc to see how people would react.
I would agree that in the 60s, and 70s, the concepts were already known, and by the 80s the hardware was good enough to do interesting things even in the home. If you take the movie Wargames, the movie is actually a pretty good reflection of what things were like then, except of course a kid wardialing into a norad system and guessing the password, and the whole nuclear operation run by an ai -- that's the only part of it fake. Although I don't know about the latter too much anymore -- there could be a government contractor today actually running things by ai, ready to be hacked -- all due to hype in ai.
Going back to running a chatbot on irc on pentium machines in the 90s: I would guess that simple program only used like 1% of CPU to have some fun. An 80s machine would have been fine for how little power they had then. Although, if an 80s machine could access the internet or some dialup terminal to a mainframe in those days, it would have been possible to have at your fingertips to have a well trained ai on like a gigabyte of memory (certainly possible in a mainframe) and do some pretty convincing things. Had the internet been a thing everyone could use in the 80s, ai would have seen as much attention then as it does now. But of course, the internet was inhabited by scientists, maybe doing a few things like this. It probably gave them a few hours of amusement, and then they just forgot about that project and moved on.