How did bots work before genAI?

I am coming from a very limited understanding of computers, so please bear with me. I'm pretty sure that long before the advent of chatGPT, some bots on Youtube, Twitter etc. were posting like humans, and it wasn't always obvious that they weren't human. Were these bots programmed with the exact things they were supposed to say or did basic genAI technology exist back them to create their texts?

Obligatory This community is for curiosity, not karma farming.