Why does the Torah not write 'Vayis'u mi'Kivros ha'Ta'avah Vayachanu ba'Chatzeros', like it does everywhere else?
Rashbam: Refer to 11:35:2:3.
Why does the Torah find it necessary to add "Vayihyu ba'Chatzaeros"?
Seforno: To teach us that they spent some time in Chatzeros. 1 Because that was when Miriam spoke against Moshe, and it was because they were still encamped there that Hashem was able to call Moshe, Aharon and Miriam to the Ohel Mo'ed.
Rashbam #1: To teach that they remained in Chatzeros until Miriam was cured from her Tzara'as.
Rashbam #2 (citing the Mechilta): When the episode with Miriam occurred, Machaneh Yehudah had already departed from Chatzeros, the Mishkan had not yet been dismantled and Moshe, Aharon and Miriam were still in the camp, together with Machaneh Levi'ah. They then recalled Machaneh Yehudah until after Miriam was cured when they finally moved from Chatzeros. 2