There was someone from CIA at that time interviewed for the (great) Netflix docudrama called Wormwood. He basically said something to that effect: we know this

There was someone from CIA at that time interviewed for the (great) Netflix docudrama called Wormwood. He basically said something to that effect: we know this substance is powerful, we don’t know what it is, if the Russians discover that it’s a mind control serum and we know nothing about it then we are screwed. Mix that (fairly reasonable at the time IMO) motivation with the… lackadaisical research ethics frameworks at the time, and the outcome gets much less shocking.