The Baal Shem Tov was a healer and a teacher who moved among people. Dov Ber, who succeeded him, did almost the opposite. He was in poor health, rarely travelled, and held court at Mezhirech in Volhynia, where the ablest young scholars of the region came to him. What he built there was a school, and it is the reason Hasidism became a movement rather than a memory.
The method was deliberate. Students were formed at the court and then dispatched, each to a territory, with the authority to establish a following of his own. Levi Yitzhak went to Berdichev, Elimelech to Lizhensk and shaped the whole Polish wing, Menachem Mendel led a group to the land of Israel, Aaron organised Karlin, and Shneur Zalman was sent into Belarus, where the opposition was fiercest. Within a generation of his death the map of eastern European Jewry had Hasidic courts across it, and nearly every dynasty that exists today traces itself to a man trained in that room.
The Vilna Gaon's circle understood exactly what was happening and moved against it, issuing bans in 1772, the year Dov Ber died. The opposition was serious, sustained and in places vicious, and it failed. An organisational insight, that a movement propagates by training and posting teachers rather than by drawing crowds, is not the kind of thing usually credited to a mystic, and it is his.