CH was back in the day a very diversified neighborhood, Bobov, Skulen and lots of others lived there. How did their shuls remain active after they left? Was the Rebbe's efforts focused on buying the shuls and keeping them open?
Encouraged local residents to daven and/or take over shuls that were "abandoned" by their congregations. This was obviously limited. But in the 80s many of the shtieblach (mostly in the area south of Eastern Parkway that remained (at least partly) Jewish. Some have been renamed and rebuilt by now. One (Kerestir) is unfortunately gone (I remember when the Rebbe went to that mikvah, when the regular mikvah was under repairs). These were mostly shtieblach in what was originally built as two family houses, multi-family building (Kerestir), or mixed-use properties (Skver).
Of the Shuls that were built as Shuls in the first place, Chovevei Torah was converted (initially partially, and later fully) into a Yeshiva building. Young Israel was demolished with condominiums built on top and a shul in the basement/ground floor. Beis Dovid Gershon resisted local Lubavitch residents, and is still controlled by the Rabbi's family that isn't local. Empire Shtieble is probably the most vibrant shul in Crown Heights other than 770. Yeshiva Reiness is part of Oholei Torah (not sure if there's a balebatishe minyan there on Shabbos & YT any longer. There definitely used to be in the 80s.
