He was actually.
As said above, I don’t think Darkside knew what the anti-life equation was yet. He might have known there was some unknown energy there and he was searching the universe for this ultimate power.
When Darkside strikes the earth in the history lesson, that is not the anti-life equation lava pattern.
I'm sorry to contradict you so much ahah, but he know what he discovered because... well, that's the moment he discovered that power exists. He came to Earth and found this equation, but before learning to master it, he was defeated. He has been looking for it ever since.
My point is that Steppenwolf had no idea that the Planet where the 3 Motherboxes were lost contained ALE Why ? I dunno, maybe nobody told him that.
That would be totally acceptable though ! He could know about the defeat without knowing further details. My problem is that it's a bit unclear.
I'm rewatching the scenes right now, to try to make a little breakthrough on all this drama ahah :
- So Darkseid found the ALE on Earth, is defeated and lose track of the planet by losing the motherboxes. Acceptable imo.
- Then, Steppenwolf arrives on Earth, called by the abandoned motherboxes. Okay, but shouldn't he wonder how these end up here? Didn't that imply a previous defeat for Darkseid? And since this one only knew one defeat, wouldn't that establish this world being the famous one hidding the ALE? Imo, we need a clarification here to know if other boxes are lost on the universe or if they are utilized as a tools, randomly planted across the universe waiting the best time to start invasions.
But it's not here.
- I thought Steppenwolf recognized the Amazons, but I was wrong, he called them first "defenders". Later, he hears them shouting "Amazons!" and from there he calls them that. So, it could work he never knew about them before and so, doesn't really know all the details from "The Great Defiance". But then, Desaad lines about the story being "well known" is
a bit misleading.
There's a way to imagine that finding motherboxes isn't that big of a deal for Steppenwolf and that he may be the guy not having all the informations because of his past treason, but the problem is that we have to assume it. Not a deal breaker for me though. Way less than the plot hole in Aquaman with a riddle dated from the moment the Sahara was still a sea finding it's solution around the character of Romulus who lived "only" 2100 years ago... Come on guys, make an effort ahah