They also have their own ripoff temple at Mount Gerazim.
Not a Christian nor a Jew; not my place to say which temple's legit and which one's the knock-off. That said: the temple on Mount Gerezim was roughly contemporary with the Second Temple in Jerusalem itself. The split was over which spot was chosen by God: Mount Gerezim or Jerusalem. Bear in mind that biblical archaeology is outside my wheelhouse; I just enjoy reading up on the sources in ReligionForBreakfast and Let's Talk Religion videos.
Important to remember that the Babylonian Exile wasn't a complete and utter depopulation of Judea, nor was it a singular monumental deportation. Tons of people stayed upon accepting Neo-Babylonian rule, with everyone exiled to Bablyon was among the upper echelons of society: scribes, priests, military officials, people from royal families. The people who weren't deported or otherwise partook in the Babylonian Exile, at least according to secular scholarship, ultimately became the Samaritan Israelites. The people who were deported/exiled were the ones who'd become the Jews of the Exile and Second Temple periods.
After Cyrus the Great conquered Neo-Babylon and allowed the Jews to return to Judea from their exile, there was a huge problem: Levites returned to build a temple in Jerusalem, but people already adapted to using Mount Gerezim in the absence of the Levites. There were stark theological and cultural divides during the Exile period. Tons of Biblical works that wound up in the Old Testament/Tanakh were penned during the late exile and early Persian periods (I think?
@Catch The Rainbow or
@Maori Kiwifruit Growers, help a nigga out here por favor). This was, at least relative to what the Samaritans had, innovative.
I'm not well-equipped to thoroughly explain the differences between Samaritan Israelites and Jews, but both groups were evolving in parallel. The Babylonian Exile, I think, is the catalyst regardless. It just so happened that both groups adapted to the Exile in fundamentally different ways. Samaritan Israelites use Paleo-Hebrew characters, whereas Biblical Hebrew is typically written with characters originally used to write Imperial Aramaic. Is one more authentic than the other? I dunno.