What made Korach do something so crazy?

Even the most egotistically minded person would have realised that his revolt against people who had been appointed by Hashem to lead the people, would certainly not succeed.
Rashi explains that Korach had some divine insight. Prophetically, he could see that in future generations, there would be household names descended from him – well known to the people, who would be great individuals – like Samuel the Prophet, and many Levites who led services in the Temple.
Korach could contemplate on what we read in Psalm 99, which we recite in Shul on Friday night, ‘Moshe V’Aharon B’Kohanav U’Shmuel Bekorei Shemo’, ‘Moshe and Aharon were amongst those who were the Priests of G-d and Shmuel amongst those who called on his name’.
And notice, say Chazal in the Talmud, Shmuel in his generation, is considered to be as great as Moshe and Aharon were in their generation. And notice as well, that Shmuel by himself, is compared to Moshe and Aharon combined. And this is the type of impression that Korach had, as a result of which he thought that he was greater than Moshe and Aharon combined.
I believe that Korach’s mistake was rooted in the wrong definition that he gave to greatness. Korach thought that to be great means, you’ve got to be famous. No. He made a terrible, fatal error.
In our tradition of course, the truly great people are those who live selflessly for the sake of others, enriching our society through their piety. That’s why the Talmud talks about the ‘Lamed Vav Tzadikim’, the 36 pious people, through whose merit the world continues to exist.
To be great means being a mensch, being there for the sake of others, whether the world knows about you or not.
Korach wanted us to remember him to this day because of his fame. Sadly, for him, we recall his name for the wrong reasons. And from him we can learn a lesson for us all, and that is, each and every one of us can be truly great.
Shabbat Shalom