It seems unlikely that all of them are charlatans (obviously some were). But, while possible, it also seems unlikely they all had schizophrenia (and even schizophrenia doesn't normally, in our current culture at least, manifest as such clear hallucinations). So I wonder how historians understand this. What is the explanation?
Or is it just viewed the same way early medieval Saint's hagiographies are viewed; we look at what it tells us about the society at the time, and basically don't bother too much about what "really" happened?
/u/sunagainstgold has talked about what pre-Dante Hell looked like and different interpretations of what angels look like and about Satan ruling over the underworld. See also this thread about Joan of Arc where someone in the comments asked about medievalists being religious. Another thread about the maid of Orleans. Also whether to take Dante seriously (whatever that means). Sunagainstgold has probably written even more elsewhere that I can't find right now.
Have you heard about Jesus' Chinese brother? /u/EnclavedMicrostate will tell you all about him! This is 19th century stuff but super interesting.