For purpose of discussion, assume that due to bad luck, this asteroid has evaded the detection of all amateur and professional astronomers until about six months from impact. The asteroid is too large to deflect with humanity's current spacefaring capabilities, and the general scientific consensus is that the impact will end all multicellular life on Earth.
What do those six months look like?
half the population would gaslight themselves into believing it's fake
25% would convince themselves it's a non issue because it would crash into the side of the earth that they're not on