“It’s always darkest before the dawn”
It isn’t. Before dawn, there’s a period called “pre-dawn” where there’s a glow on the horizon from the approaching sun. This is the ~hour-long period between astronomical sunrise and actual sunrise. And it’s fairly bright. That’s why astronomers make a distinction between astronomical sunrise/sunset and actual sunrise/sunset – because the light from the sun in this period is enough to interfere with astronomical observations.
So, to summarise, just before the dawn there’s a period of dim light which is actually as bright as the night gets before actual daytime (barring things like supernovae). The darkest part is around midnight when the sun is on the opposite side of the planet. It’s not always darkest before the dawn, it’s darkest before the period of light before dawn. And in fact that’s not even “darkest”, because you have things like stars and the moon lighting things up. It’s actually darkest in caves, where there is no dawn.
But who lets facts get in the way of a bland metaphor?