Youtube is just adapting to make what they publish generally more suitable for ads. The relevant model here seems to be Edward Herman's 'Propaganda Model' ,
which is generally considered to be about news and claims that news media are mainly following business logic: they adapt to get along with their advertizers, with government sources, with powerful players that could harm them. The result is that media are very compliant with the dominant powers and that journalists are selected for how well they fit into that system.
With youtube it's kinda obvious because they don't have any high principles to uphold but news media deny it claiming they're above all that.