The Chasam Sofer says in the name of the של״ה הקדוש that the two-hundred and fifty followers of Korach did not fight for the same reason as him. In fact, they fully agreed with Aharon Hakohen being the Kohen Gadol, they just argued that even common folk should merit to take part in the avodah in the Mishkan somehow. He compares them to נדב ואביהו, who did something wrong, but it was an outgrowth of an overriding desire to be part of the holy avodah.
The אור החיים הקדוש specifies that it says that Korach and Dasan and Aviram went to stand before Moshe, and challenged his G-d given leadership. The other two-hundred and fifty men did not go as far as to actually stand before Moshe. Though they agreed with Korach somewhat, they actually had a different plan, with different intentions. They did not seek to challenge Moshe and Aharon, in as much as they sought to establish that every person should be given an opportunity to be part of the avodah. Though their intentions may have been pure, the sin was still grave, and there was no justification for them joining a machlokes. Because their intent was different to that of Korach and the main agitators, they did not meet the same demise. However, because they joined a machlokes, regardless of their intention, they were consumed by a holy fire. (see חתם סופר עמ' צא ד״ה זכרון)
This is in fact what the wife of און told him. Your compatriots hope to be part of the avodah in the Mishkan, however because I have uncovered my hair, you will either way not merit that. With this extensive plan and reasoning, she saved him from a terrible fate.