Earlier discussion, similar topic, that wandered well...
2016 By The Ad Business, Cre8, February 2017.
The fascinating point of the OP linked report is that the stats are from a particular constrained filter bubble: (1) news sites, (2) only the main domain for each, and (3) only those main domains with minimum 10-million/month uniques during time period.
Note: musing - how do they account for bot traffic?
And, given that many/most of the largest news organisations have given up on 'own' advertising sales it further defaults to third party ad networks, which - surprise! - defaults to G and FB.
What is totally missing are what are probably the ad networks greatest fears: own ad sales (mostly smaller sites these days and mostly not primarily 'news' sites) and 'native' advertising. The web has been changing greatly over the past few years (too too many are catching up to what some few were quietly doing over a decade ago) and chronic ad fraud within and without the ad networks is accelerating the shift.
Few/none are writing about it because it mostly does not involve the dominant dinosaurs. Plus, both sides, advertiser and publisher, retain significant competitive advantage from remaining below the web's general radar. However, doubling year over year eventually owns the board.