Because the Media companies like YT get their revenue through advertisement. They created an algorithm to encourage people to watch more content. Watching more content means more ads which means more money for youtube.
Their algorithm learned that people kept watching content as it escalated and became more extreme. As an example, you might go from watching a game channel, to watching a gamergate video, to watching Sargon of akkad, to Ben shapiro, then to stephen molynoux, then to stormfront.
So for years, YT made money off of showing people increasing extreme/radical right wing content irrspective of its factual accuracy.
Youtube (and other sites like Facebook) within the last 3 years have been put under a lot of pressure as this platform for radicalization became more well known. As a result, Youtube was pressured by the public and advertisers to not advertise on controversial videos, and in some cases, remove extremely controversial videos.
