When Moshe commanded not to keep the mon (manna) overnight, there were people who did. Rashi tells us this was Dasan and Aviram, who would later join with Korach in his fight against Moshe.
Then, some of the people went out to collect mon on Shabbos, thus desecrating it by carrying baskets out to do so. The Sefer Matamim says this was because Dasan and Aviram, in their quest to discredit Moshe, had scattered their Shabbos day provisions in the desert.
Because the birds ate it (which is why there is a custom to put food out for them on Friday) when the people went to collect it, there was none.
Then, Hashem asked Moshe, “How long will this nation refuse to listen to My commands?”
If it was once again Dasan and Aviram causing the problems, why does Hashem blame the whole nation?
The answer, based on a speech of R’ Elya Meir Bloch z”l, is that if the nation was on the right level, Dasan and Aviram would have been too embarrassed to do what they did.
Because they felt emboldened to speak and act against Moshe, it must be that the climate in the camp was one that allowed such rebellious dissent.
Therefore, Hashem rightfully assigned culpability to everyone.
It's a lesson for us to not tolerate things that should not be accepted, or else we are all to blame.
