Judea is the highland country around Jerusalem and Hebron, and it is the smaller and poorer of the two Israelite kingdoms of the Iron Age. It outlasted the other. Assyria destroyed the northern kingdom of Israel in 722 BCE, and Judah survived as a vassal for well over a century afterwards, which is why the surviving religious literature is Judahite and why the words Jew, Judaism and Judea all come from its name.
The reforms attributed to Hezekiah and Josiah belong to this territory, and they are the point at which a religion of one god among others becomes a religion of one god only, with sacrifice restricted to a single sanctuary in Jerusalem. Whether those reforms happened as described, and how much of Deuteronomy was written to justify them, is a central question of biblical scholarship.
After the exile Judea returned as a temple province under Persian, then Ptolemaic and Seleucid rule. The attempt of Antiochus IV to suppress the cult produced the Maccabean revolt and an independent Hasmonean state, which was then absorbed by Rome. Herod rebuilt the temple on a platform so large that it remains the defining feature of Jerusalem's old city. Two revolts against Rome, in 66 and 132 CE, ended the temple and then the Jewish presence in the region's centre, and forced the religion to reconstitute itself without either.