A long blog post on Olivier Ertzscheid’s personal website [in French] tackles the ideological orientation of the major social media platforms from a variety of points of view (the political leanings of software developers, of bosses, of companies, the politics of content moderation, political correctness, the revolving door with government and political parties, the intrinsic suitability of different ideologies to algorithmic amplification, and so forth).
The conclusions are quite provocative: although algorithms and social media platforms are both demonstrably biased and possessed of independent causal agency, amplifying, steering, and coarsening our public debate, in the end it is simply those with greater resources, material, social, cultural, etc., whose voices are amplified. Algorithms skew to the right because so does our society.