This is the most concise explanation of the effect and impact of CDA 230 that I've seen.

(from Bower & Zittrain, 2020: https://misinforeview.hks.harvard.edu/article/content-governance-in-an-age-of-disinformation/)

Answering impossible questions: Content governance in an age of disinformation | HKS Misinformation Review

The governance of online platforms has unfolded across three eras – the era of Rights (which stretched from the early 1990s to about 2010), the era of Public Health (from 2010 through the present), and the era of Process (of which we are now seeing the first stirrings). Rights-era conversations and initiatives amongst regulators and

Misinformation Review