The Elephantine community identified as Judeans, spoke Aramaic rather than Hebrew, and were in regular communication with Jerusalem and Gerizim. As Granerød notes, the community was not an isolated outpost stuck in a time warp:
And Kratz:[T]he Elephantine community stood in contact with Jerusalem. Although Elephantine was located on the traditional southern border of Egypt, it was not an isolated outpost on the fringe of the world. The Nile was navigable all the way from the Nile delta to Elephantine. A journey from Elephantine to Jerusalem might take approximately one month. In comparison, according to the Bible it took Ezra around four months to travel from Babylon to Jerusalem. In terms of travel time, the Judaeans in Elephantine were much closer to Jerusalem than was the priest-scribe who is often accorded great importance in the (re-)formation of Judaean religion in the Persian period. Whereas this may indicate potential contact and demonstrate that the historical-geographical conditions for travelling between Elephantine and Jerusalem were more favourable than those between Babylon and Jerusalem, it is also evidenced by documents from Elephantine that there was actually a two-way contact between Jerusalem and Judah (and Samaria). Not only did the Judaeans in Elephantine know the names of the tenuring governors of Judah and Samaria (in this case, even the names of the sons of the governor) and the high priest in Jerusalem (cf. A4.7 par.), they also wrote letters to them and even got a reply (although the Judaeans in Elephantine regret that the Jerusalem high priest and his colleagues did not respond to their initial letter).
[T]he Elephantine documents are contemporary sources and probably even more representative of the lived and practiced Yahwism of the Persian period than are the biblical texts. (Dimensions, p.4f)
As someone else said, if the finds at Elephantine had come to the scholarly community's notice much earlier with time to digest and engage with, it is possible that the Documentary Hypothesis of the Wellhausen model might never have been born.Likewise, the mission of the ambassador Hananiah bears witness to close contact between the Judeans of Elephantine and those residing outside Egypt. In a certain sense, he constitutes living proof for the situation at Elephantine being actually representative of many—if not most—portions of contemporary Judaism. Although Hananiah was himself a Judean, coming from Judah or perhaps even the Babylonian diaspora, and should therefore represent biblical Judaism of the post-state period (to follow the usual scholarly explanation), he called the thoroughly unbiblical Judeans of Elephantine his “brothers” without any reservation whatsoever. Two conclusions proceed from this state of affairs. First, the Judaism of Elephantine existed not at the edge of the world but in close contact with its Jewish brothers even outside Egypt, as evident in the correspondence concerning reconstruction of the temple and in the mission of Hananiah. Second, the Jews in the motherland, i.e., Yhwh-devotees in Samaria and Judah, raised no objection at all to their brothers at Elephantine—at least as far as we can see—nor did they distinguish themselves from them in either essence or kind. (p. 146)