Or HaChaim on Numbers 14:1/אור החיים על במדבר י״ד:א׳

1 ותשא כל העדה…ויבכו העם, And the whole community raised their voice and the people wept. The Torah adds the word "and the people," and did not content itself with reporting those who raised their voices. This is to tell us that it was not the whole community which wept on that night. The entire nation raised their voice (against Caleb, etc.) after the spies had succeeded in inspiring fear in them, but only part of the people actually wept.

2Another method of interpreting this verse is based on Sotah 35 and Taanit 29. According to the Talmud, G'd told the people that seeing they had wept without good reason on that night (the 9th of Av), G'd would give them adequate reason in the future to weep on that date (the annivesary of the destruction of the Holy Temple). The words: "the entire community raised its voice," is an allusion to the unwarranted raising of their collective voice which eventually resulted in the people who lived during the destruction of the Temple weeping over its loss. Had the Torah simply written: "the people wept on that night," we would have understood this as referring to the people who had raised their voice at the beginning of the verse.