I'm curious how Fox News chose to push for denial rather than, say blaming it on international or ideological opponents.

Perhaps it's just that they can change course without any pushback from their demographic -- they're happy believing that we've always been at war with Eastasia. Still, it must cost them something to be quite so demonstrably wrong on something that's so much in people's faces. (As opposed to, say, climate change, where the effects are much slower and more easily shuffled under "the heat wave and fires are just weather".)