>Do you believe they abandoned that pursuit after a failed experiment 50 years ago?

I believe direct mind control of that sort is infeasible, certainly likely impossible at the scale of entire populations, so I do believe they abandoned that specific pursuit after discovering that the human brain and LSD didn't work the way they hoped. The government also looked into remote viewing and psychic assassinations, but I don't believe they just kept on trying that either.

>Do you believe they abandoned it forever?

The goal? Probably not. The means? Probably. I believe it's more effective in modern society to influence people through disinformation campaigns and popular culture, particularly though social media, than attempt to control them like puppets by secretly dosing them with LSD and barbiturates.