>Where does the revenue come from again?
Ad revenue. Even if these companies don't collect money from the political astroturning, they receive increased traffic and engagement. Those are two of the biggest factors in online ad revenue.
>Anyway, I think a lot of people will be more influenced by a targeted video ad than a random post on reddit. But that's like, just my opinion.
I don't know. People have gotten pretty good at tuning out marketing when they know they are being marketed to. That is why word of mouth support can be so important. On social media it is getting very hard to identify marketing. I would bet seeing dozens of comments a day about how "Clinton is untrustworthy" would be more effective than hearing that same rhetoric in a video that starts with "I am Donald Trump and I approve this message."