From Chabad.org: Moshe pleads with G‑d not to accept the incense offering of the rebellious group. Korach spends the night inciting the Jews against Moshe, and gathers them all to the entrance of the Tabernacle to witness the grand spectacle. G‑d’s glory appears.
Korach’s complaint to G-d was that upon leaving Egypt they were promised this land flowing with milk and honey, and they never got it. And now they were told that they’ll end up dying in the desert. But had they listened to the right spies, they would have realized that they were actually so close to entering this promised land, and they chose to believe the negative spies, instead of the truthful ones. Yet they were so convinced that they chose correctly that in THEIR mind they were never offered a flowing land. It’s scary to think of how the mind will warp reality to make it fit its thoughts, with sometimes total disregard for actual reality. In this case we have the perspective to realize the mistake, and perhaps learn from it.