Clarification:
There were no “satmar chasidim” in 1900. The satmar rov was 13 at that time. His first position as Rav was in 1911 in Austria, where he was a rov, not a rebbeh with chasidim. He became rebbe in satmar in the late 1920s.
And of course, the claim that anyone ever thought he was moshiach is baseless. This “banner” was most likely the result of reading a word quickly and associating it with a word seen often before. This happens to me as well, for instance I’ll see the word “jewelry” and think it’s “jewish.” Having been exposed to messianic literature and signage for decades, CS probably misread whatever this banner said.