Seeing as the Cloud had departed from the Ohel Mo'ed (See Pasuk 10), why did the people not travel?
Seforno: Because they realized that the Cloud only departed in order to distance Miriam. 1
On what merit did the entire amp of Yisrael wait seven days for Miriam to be cured before moving?
See Ba'al ha'Turim.
Targum Yonasan: From here (the fact that the whole of Yisrael -numbering 600,000 - the Clouds of Glory, the Mishkan and the well, waited for Miriam for seven days), we can learn the great reward that is due to Tzadikim for every Mitzvah that they perform.
Rashi: See Sh'mos, 2:4.