I seriously doubt there is any "algorithm". And, there are simply too many videos or ads on Google for a human to review everyone of them. The clue to what happened is in the article:

The report notes the campaign videos generally ran over the summer but were taken down by the companies after only a few days.

The key is "after only a few days". Social media companies rely on crowd-sourcing to do at least the initial screening. An employee doesn't get involved until enough users hit the "report" or "complain" button. Then, they might look at it, but are more likely to simply remove/block the content until the originator files an appeal.

Per Pew Research in the last year or so, a leftist is more likely to hit the report button over something they disagree with, while a conservative or moderate will just ignore it. This is why conservative content gets targeted, and as conservatives quit the platform in disgust, it turns into a leftist echo chamber.