The other was that it enabled the political news media to restore their damaged perceived credibility by blaming foreign meddling as an excuse for their poor / echo chambered reporting of where their respective countries were at.
In the case of the US, the political news media was correctly reporting that the American public preferred Clinton to Trump.
Neither case should have damaged their perceived credibility, except in the minds of people who believed that there was a conspiracy of under-reporting the popularity of Brexit and/or Trump.
[0] https://en.wikipedia.org/wiki/File:UK_EU_referendum_polling....
The sudden swing towards leave does not seem to represent a failure in polling (or media) but rather a demonstration that Facebook's dark ads platform alone can subvert the ability of a high-functioning democracy to make an informed, fact-based, decision on a question that will impact generations of people.
That should terrify a lot more people than it does.
[1] https://www.joe.co.uk/news/brexit-facebook-adverts-192164 ; https://www.channel4.com/news/factcheck/factcheck-vote-leave...