Apparently the phrase first showed up in 1968, but “drinking the koolaid” is more strongly associated with the Jonestown mass suicide in 1978, wherein 900 cult members all drank cyanide-laced Flavoraid, including young children, and the audio recordings of that event are haunting.
koolaid was always an expression for “getting drunk from the propaganda”
Apparently the phrase first showed up in 1968, but “drinking the koolaid” is more strongly associated with the Jonestown mass suicide in 1978, wherein 900 cult members all drank cyanide-laced Flavoraid, including young children, and the audio recordings of that event are haunting.