And the people who run the "non free speech" platforms (i.e., all the popular ones) are operationally "opposed" to free speech primarily in the sense that they want a pleasant platform for advertisers, and hence must stifle the stuff that's unpleasant to advertisers. There is some personal ideology at the top of these organizations, but it is extruded through a profit seeking filter and often barely survives operationally intact.

I don't say this to excuse their actions or say that this filter is good, but that seems to be the fundamental mechanism.