Legitimately, what else would they use? Hardly anyone uses Mastodon - I don't for sure, but from what I hear, the devs continually ignore the needs that people keep asking about. Which is why so many turned to Bluesky - it works.

To discuss the Threadiverse that I am much more familiar with, literally 100% of the people that I've told about "Lemmy" have outright chided me for having told them about it. (1) If you Google'd that term (not DuckDuckGo, I'm talking mainstream normies here) a year ago, it would take you to lemmy.ml; (2) that instance by default does not show All, but rather Local; (3) lemmy.ml - along with lemmygrad.ml and hexbear.net - routinely calls for the murder of everyone participating in a capitalist, Western society (Edit: not just billionaires, or even millionaires, but anyone who participates). And showing Local rather than All does not dilute that flood as much as you see your view of the Threadiverse content from lemmy.world. (4) no major Lemmy instances defederate from lemmy.ml (quokk.au did iirc, before it switched all the way over to PieFed).

There are some MAJOR structural issues with the Fediverse that need to be solved first, before mainstream normies - who remember are primarily centrist (aka liberal to even right-wing by the standards here) - will feel comfortable here. Not celebrating and calling for their literal irl murder might be a start. (Note that while YOU might have such communities and user accounts blocked, a guest account, especially browsing lemmy.ml, cannot and would not know how to deal with such - e.g. a new account on most instances could respond to comments in Chapotraphouse@hexbear.net while browsing All and have no idea what they are walking into... then noping out and worst of all, telling everyone that will listen how extremist we are here)

We are a Nazi bar here, except instead of Nazis it's tankies. Also, purity beatings will continue until morale improves. Mainstream people do not feel welcomed here. And most people seem unable to even say so much as they should be? Would you want more "right-wing" people here? (I actually mean centrists, but especially in the USA where so many are located, that is more where they would lean, right?)

Edit: so to answer your question, they use Xhitter the same way that we use the Threadiverse - by blocking early and blocking often, and putting up with what the remainder of stuff that they do not like, in order to make some use of what is freely offered to them, especially requiring minimal efforts to overcome their existing inertia.