Why does it say that they will know that Yisrael were exiled due to their sins?
Rashi: When they see My power, they will recognize that I did not refrain from saving them due to lack of strength. Rather, "due to their sins I hid My face from them", and they were exiled.
Malbim: Initially there was Chilul Hashem (a) due to Galus ? they said "Am Hashem Eleh ume'Artzo Yatza'u" (36:20). (b) In Galus itself, there was Chilul Hashem. Several times they were 'sold' to be slaughtered and killed, and Hashem did not save them. They will recognize that I made these decrees.
Will they all fall to the sword?
Radak: No; [it says Kulam because] the majority will fall. This is like "v'Chol ha'Aretz Ba'u Mitzraimah" (Bereishis 41:57) and similar verses.