I’m going to put myself in an impossible position and actually defend Korach here. Now, he was definitely a demagogue and a rebel against the authority of Moshe and ה׳, but there’s something deeper worth looking at:
The Midrash expands on Korach’s complaint of כל העדה כלם קדשים and connects it to the previous parasha:
The analogy is clear: just as a garment of techelet shouldn’t need an extra thread of techelet to make us remember the mitzvot, and a room of sefarim shouldn’t need one more tiny scroll, so too an entire nation that heard G-d’s voice at Sinai doesn’t need another prophet to tell them His word.
And we are sympathetic to his claims. As Rabbi Sacks says:
But how could he dare to go against Moshe after all the miracles that had taken place? Rashi explains:
Samuel is considered equivalent to Moshe and Aharon in the chapter of תהילים we say Friday night:
And the sons of Korach are explicitly mentioned as having survived their father’s rebellion in Parashat Pinchas:
But is this שלשלת גדולה, this great chain, that Korach sees himself a part of? For that we have to look at דברי הימים
And it is the wording of the Torah that makes it clear that Korach considers himself part of a chain: דתן, אבירם and און are named in the usual fasion: with patronymic and tribe. Korach is named father after son for four generations, and the Torah might have gone further:
The Midrash makes the connection even stronger:
This is an astounding midrash. It sees the roots of Korach’s rebellion in his ancestors, who were all great צדיקים. I think the explanation is what we mentioned before: Korach’s claims that we are all equal before ה׳ are true. We need to protest when those in power abuse that power. And the lineage of Korach embodies that principle. We first see that in the story of לוי and דינה, when he and שמעון rescue her from שכם. Jacob is concerned about אַ שאַנדע פֿאַר דער גויים: (בראשית לד:ל) ויאמר יעקב אל שמעון ואל לוי עכרתם אתי להבאישני בישב הארץ. לוי and שמעון respond: there is an injustice, we have to fight: (בראשית לד:לא) הכזונה יעשה את אחותנו?
The chain culminates in Samuel, the descendant of Korach. The Gemara discussed what happened when he was first brought, as a young child, to עלי the כהן גדול:
What’s the big deal about not waiting for a כהן to slaughter the sacrifice? Does that warrant the punishment of a little kid? There’s a backstory here:
So the “waiting for a כהן” was a symptom of the corruption of the משכן and the כהונה. Samuel was making the same claim as Korach: כל העדה כלם קדשים, so שחיטה כשרה בזר. He was challenging the status quo, the entire power of the כהנים. And he would become the נביא of the destruction of the משכן and the כהונה:
And his descendants would become the new leaders of the prayers in the בית המקדש, the בני קרח. Their psalms mostly talk about the glory of Jerusalem, but some reflect this instinct to fight unjust authority, that we are all equal in the eyes of ה׳:
Moshe himself was disciplined for not respecting this aspect of Korach’s rebellion:
Korach himself needed to be fought; he wasn’t really fighting for the “common man”. But the sentiment expressed in his words was part of his “genetic” makeup and Moshe should have respected that. The claim of כל העדה כלם קדשים was not רב לכם, too much to strive for; it in fact is the goal of the Torah outlook and how we each should see our role in כלל ישראל.