Haven't there been numerous recent leaks detailing how Google has let revenue team take over from the search quality team over the past few years? [1] They can adjust auction parameters for owned properties to juice CPCs, blend ads to drive CTR and disable functionality of ad-blockers in tranches to squeeze as much growth as needed. Search quality has seemed awful for quite some time [2], but all that really matters is growth for ad ePM-- driven by CTR and CPC. The leaked documents from last year also had comments about correlations between lower search quality and higher ad click rates, so there is that, too.
Youtube also increases ad load. More ads per video, combined with organic growth, higher engagement and wider distribution (smart TVs probably have insane metrics-- plus no real ad blockers there, either) mean they'll keep having display/video ads doing extremely well, too.
[1] https://www.techspot.com/news/102765-who-prabhakar-raghavan-...
[2] https://methodshop.com/why-google-search-sucks/