Common sense? Does it seem likely that politicians concluded being able to manipulate people better = improvement to democracy?

Hmm, actually, you may have a point.

Wearing seatbelts?

Drinking less alcohol?

Eating well?

Not beating your wife?

Voting?

Finishing school?

Recycling?

Most of the ways our government wanted us to change in the last century were fairly positive and actually barely controversial.

It's the controversial one's we talk about.

I am not entirely convinced myself (I doubt there was a conspiracy so much as shared incentives) but the documentary is quite compelling, I recommend it.