Korach son of Izhar son of Kehas son of Levi took... (Num. 13:27)
Korach possessed many outstanding qualities. He hailed from a distinguished family, and was a wise man. How could he fall so low as to accuse Moshe of selfishly taking power and prestige for himself? The Torah testifies about Moshe, "Now the man Moshe was exceedingly humble, more than any person on the face of the earth." How could Korach possibly accuse him of seeking honor!?
There are two types of people. There are givers - people who are constantly looking for opportunities to assist others, and there are takers - people who are continuously looking to further add to their possessions, to satisfy their own needs and obtain more honor. The takers are never satisfied; they always desire more. At the very beginning of Korach's story the Torah reveals the root of his downfall: "Korach took." -- Korach was a taker; he wanted more honor for himself. Even though he was already privileged to be in the tribe of Levi, that wasn't enough for him. He needed more. He wanted a prominent communal position and was jealous of the honor that Moshe and Aharon were getting. His jealousy knew no bounds and Korach did whatever he could to obtain that honor, even though it meant starting a rebellion.(1)
When someone is self-centered and has a particular desire, his intellect may get corrupted, preventing him from thinking rationally. Blinded by this desire, he will do anything. In order to avoid such a downfall he should work on assisting others and become a giver.
1. R' Yaakov Eliezer Schwartzman.