Nobody ever accused these companies of being competent at suppressing the research (which includes third parties btw, not just internal).

Companies do this research for all sorts of reasons (including legal compliance, demonstrating due diligence to regulators, to understand users and improve products, etc etc etc). For example, it's not like Zuck commissioned an internal study to show how they're harming children, more like some internal team was seeking to understand why kids love a certain feature which led them to conclusions that make the company look bad.

To your third point, that research is usually leaked by whistleblowers or conducted by third parties, not because of the altruism of these companies.

Finally, the platforms aren't doing enough and with this court case, it seems like they've persisted in finding ways to hook children because of financial incentives.

The sources cited in this article are a good primer for understanding what these companies are doing: https://www.transparencycoalition.ai/news/meta-suppressed-re...