The op doesn't seem to know the first thing about advertising and is in denial of how it works.
Op asks head of facebook advertising if advertising influences people, their response "No companies spend millions on advertising with us because it doesn't work!".
> The gullibility of the latter two may have stemmed from wishful thinking: If Brexit and Trump could be traced to the malign influence of a single company
The media picked Cambridge Analytica as their keyword for the story but both Brext and Trump campaigns used more than one ad agency.
> most ad insiders express skepticism about Cambridge Analytica’s claims of having influenced the election
Citation needed. As an ad insider I know first hand that the tactics used by Cambridge Analytica and other agencies work, thats why people pay me to do it.
> and stress the real-world difficulty of changing anyone’s mind about anything with mere Facebook ads
Well no of course not, advertising cant change anyone's mine, thats not how advertising works.
You target people who already have the mindset and encourage them to act on it. Thats what ad men like me do and we keep making good money doing it because it works.
The whole tinfoil hat thing is a bit dramatic for my liking the reality is that if advertising didn't work people wouldn't pay for it.
Every election has millions spent on advertising to influence the result, thats the truth not some tin foil hat conspiracy.