Somewhere I saw the Tur Shimon case attributed to the cessation (bitul) bais medrash shabbos, that they would daven in sush a time and way that there were long lecture or study sessions up to chatzos. (like the case of Rav doresh on YT in Bezah.
RE: “there were no eruvin” A moomcheh told me that in Europe, there were those who kashered an eruv where there were utility poles with the wires on crossbars. It could be there was someone with broad enough shoulders that might have paskened that way for East NY, the “little Jerusalem” that it once was.