YouTube decided that it will demonetize videos. They preferred to do that for some complains by some Advertisers, rather than giving Advertisers tools to avoid/select certain channels or certain topics. Very similar concept to AdWords, BanWords! Put the Advertiser in control of where the Ad gets shown or specifically, where it doesn't get shown. Demonetization was an ideological decision by Google, it was a political decision.

>As such, every non-monetizable video hurts YouTube's bottom line.

Even every non-monetized video is still eyes on the screen for Google. NetFlix claims to compete with books & libraries for time of the day from its viewers. Yeah, Google may not show Ad on that video but the next one in autoplay/recommended list is still going to ring the cash register. It is actually better for Google because they may very well show Ads but not pay the De-Monetized content creators, videos that they created actually act as leads to youtube. These political videos is where a reader is sent to youtube from non-youtube sites, which is much more valuable to google and they are getting away by not paying anything for that. Leading video is much more valuable to google than a video in auto-play list. Not pay for leads but get paid for Ads on subsequent videos, very nice business model win-win Google developed for itself.