I think it is more true that political polarization is used to make ad targeting more effective. Almost nobody uses Facebook to drive opinion or do "branding."

I think it is more true that political polarization is used to make ad targeting more effective. Almost nobody uses Facebook to drive opinion or do "branding." Instead, they let Facebook target some campaign to the audience that maximizes ROI. All of the political Facebook ads you saw last year were fundraising ads, and the small net yield (revenue generated minus Facebook cut) was used on other platforms to pay for ads attempting to sway the few percentage of the electorate that was persuadable. Similarly, Exxon is paying for some sort of action on the part of the targeted consumer, not trying to change minds.