Often times, one sees people who start off with relatively reasonable, mainline positions, who become increasingly strident and radicalized as a result of writing something that sets off the terrible, toxic, troll-ish wing of our community. It's a feedback loop: they are attacked relentlessly, which makes them view the side that's attacking them with greater hostility, which encourages them to relate to that side even more pugnaciously, which encourages still more attacks, until we end up in a state of full-on hostility.
One place you often see this is persons who criticize racism in the Jewish community. If their post gets any attention at all, they will invariably experience a vicious, terrible pile-on by the nastiest elements of the Jewish right, who will attack them as fake Jews, as Farrakhan-esque, as anti-Zionists (this will occur even if their critique doesn't mention Israel at all). Another place one sees it is with collegiate Jewish students who attack Jewish exclusion in progressive spaces; these persons will often find themselves savagely assailed by the trolly elements of the Jewish left, accusing them of being fascists, colonizers, and Israeli stooges (again, this will be true regardless of whether the criticism says anything significant about supporting any particular Israeli policy).
In either case, once the controversy becomes recognized as the latest front in the forever-war between the terribles on the Jewish right and the terribles on the Jewish left, everyone will quickly assume their assigned places -- attacking the new "enemy" or defending the new "comrade". And since people naturally dislike being attacked and like being supported, the result is that a person who started in a perfectly normal and mainline position will often quickly find themselves radicalized in whichever direction has not been loudly comparing them to pond scum for weeks on end. This is why one ends up seeing folks go very quickly from, say, somewhat ambivalent liberal Zionist to "FROM THE RIVER TO THE SEA" in the space of maybe just a few weeks; or on the other side go from "still with her"-style Democrat to "Critical Race Theory is an existential threat to Western Civilization!" in a similar time frame. It's a function of recoiling from who hates you, and liking the people who like you. Nothing especially complicated about it.
The thing is, though, that for persons who start in relatively reasonable, mainline positions, there's a sort of arbitrariness as to which direction they go. Many of the people I have in mind here, at the proverbial T1, probably could have written a post or essay or tweet that tweaked off either side. They would be critical of racism in the Jewish community and they'd be sensitive of Jewish exclusion in campus spaces; they'd call Netanyahu a bigot and they'd say SJP had made their campus a hostile environment. Which comment sets off the landslide is, more or less, a coin flip. Any one of them could have easily gone either way, just depending on for whom they become the symbol of 20
minutes hours days of hate. But perched on the knife's edge, it takes a lot of discipline to avoid falling in one direction or the other.