Your own scenarios exhibit this, for example:

- You ask if the far-right are magnitudes more vocal, ignoring the comparison to the extremely vocal far-left which is heard regularly on mainstream social media

- You conflate "conservative" with "selfish", presumably ignoring the selfishness of the extremes at both sides.

Frankly, I think the left (and by extension, most social media sites) are WAY more comfortable with censorship, banning, hiding, etc., especially of ideas that don't align with the left. (Typically characterized as "evil".)

The far-right, on the other hand, I think is a lot more tolerant of at least the notion that "other" speech exists. They'll insult you, make fun, etc., but the compulsion to censor others is far less frequent.

So when you have a whole segment of the political spectrum treated as evil and silenced, they tend to gravitate to fora that enable speech, even if unpleasant speech. The far-right might be most noticable on those platforms, but if you look carefully, you'll see a whole gradient of right-ness.

And even some lefties!