God in His wisdom chose Moses to be the leader of the Exodus. He was consistent with His Word. For the Word comes to the prophet.
Korah, Dathan and Abiram had other ideas. They challenged Moses. Surely he was not the only holy man. All the congregation of Israel (Israel was the church in the wilderness) were holy.
This was true. For all of Israel was under the blood of the atonement. The lamb/heifer/bullock died for them.
But the same God that provided an atonement also specified a prophet-leader. To reject that under any guise was to reject the leadership of God in that age.
Korah et al, discovered the consequence when the ground opened and they and their entire families (followers) were buried alive never to be seen again.
Those who hide under the umbrella of the Atonement and reject the Word-prophet, will find themselves soon buried in the earth’s bowels.