Originally Posted by Deathstroke
It's also the fact that Darkseid is incredibly similar to Thanos.
And Marvel already teased Thanos this way in Avengers, and billions of people already saw that film and have that teaser in their minds.
I don't know about billions, but a lot of people dis see a glimpse of him at the end credits of the film. I don't know if most of them knew who he was though.