After the destruction of the 2nd temple and Jerusalem, when, where and how did a new centralized leadership arise?

Question

In other words, without a locus, polity or centralized worship, when and how did cohesion and order get reestablished from the chaos after the Great Revolt Circa 70 CE?

Answer 1

Though I'm not sure this question is on-topic for this site, the Talmud in Gittin 56b tells us that during the Siege of Jerusalem, Rabban Yochanan ben Zakai sneaked out of the city, met with Vespasian and impressed him enough to be allowed to strike a deal with him:

"Vespasian then said to Rabban Yoḥanan ben Zakkai: I will be going to Rome to accept my new position, and I will send someone else in my place to continue besieging the city and waging war against it. But before I leave, ask something of me that I can give you. Rabban Yoḥanan ben Zakkai said to him: Give me Yavne and its Sages and do not destroy it, and spare the dynasty of Rabban Gamliel and do not kill them as if they were rebels, and lastly give me doctors to heal Rabbi Tzadok."

Vespasian agreed to this, and thus the new court, sometimes called "Kerem b'Yavne" ([a] vineyard in Yavne, because of the way the sages sat - in rows, as opposed to a semi-circle before the destruction of the Temple), was set up and simultaneously, the lineage of the Nessi'im - princes - was also saved (the aforementioned "dynasty of Rabban Gamliel") and continued on as leaders in Yavne. Any surviving sages of the Fall of Jerusalem escaped to Yavne and other towns and cities, in particular in the Galilee.