The causal relationship here would be extremely interesting: Do those individuals start off with brain that is slightly differently wired than the "normie" population and become lonely because they just don't vibe well with them? Or is their loneliness causing their speech and thought patterns to diverge, because they have less opportunities to "resync" with the mainstream culture? Or a sort of feedback loop of both - or something else completely?

I can say from direct anecdotal experience that being excluded leads to being even more excluded in the future unless an outside force intervenes. Social skills, speech, belief in the ability to be understood by others are things that need honing and proofing by experience. The less you have of them, the less meaningful opportunities to improve them you get.