Zack Snyder's Justice League featured a totally different take on Steppenwolf, and the Snyder Cut spent a little more time exploring the villain's relationship with Darkseid. Throughout the course of the movie, it became clear that Steppenwolf had been banished from Apokolips and tasked with travelling from planet to planet searching for the Anti-Life Equation.
We never learned exactly why Steppenwolf had fallen out of his nephew's good graces (there were hints at some sort of betrayal), but in an interview at Justice Con, Snyder finally shed some light on the dynamic between the two characters.
"I feel like there was a coup sometime...a small coup attempt," Snyder explained. "I don't know how involved Steppenwolf was. I don't think he was deeply involved or the 'kingpin,' but certainly there might have been a negotiation that he was involved with. He slaughtered those [traitors]; he responded correctly, but in that small hesitation...I don't think Darkseid was down with the notion that there would even be a hesitation."
It's interesting that Snyder has this mental history of his SnyderVerse, but decided against including any of it in the movie itself (especially as it would have better explained Steppenwolf's motivations).
Ultimately, Steppenwolf was beheaded by Wonder Woman and his skull was crushed by Darksied. There was no coming back from that, and it's unlikely his history would have been referenced in Snyder's planned sequels. Still, these comments address what many fans felt was a plot hole in the four-hour cut of Justice League, and that's definitely something to be grateful for!
Zack Snyder's Justice League is currently streaming on HBO Max.