While the story of Cain killing his brother may be commonly known, the rebellion led by Korah is quite obscure.
Korah was from the tribe of Levi; he and the other Levites were assigned God-given tasks to serve in the temple; they were set apart for this. However, they were not to serve as priests; that fell only to Aaron and his descendants.
Korah didn’t like these distinctions; he advocated all people were holy, had God (the Holy Spirit) in them, and should be elevated to the level of priests. (Interestingly, these were something that Jesus would later proclaim and that his followers would embrace, but in Korah’s time, this was not the case. There were distinctions and that’s how God wanted it at that time.)
Korah stirred up some followers, insisting on equal status for all. Then he and Moses had the equivalent of a modern-day smack down. Moses won and was affirmed by God; Korah lost — big time; the ground beneath him opened up and he and his family fell in and died.
Today, we would hail Korah as a martyred reformer who pursued justice and equality, advocating that anyone can approach God.
Although Jesus would later usher in these changes, that is not what God had put in place in Korah’s day. He had a different plan and, no matter how well intended, Korah opposed it — and will forever be associated with a failed rebellion against God.