With the Justice League helping to pick up the pieces, blame has been placed at the feet of Lex Luthor and “his associates,” which might mean the Legion of Doom teased at the end of Justice League’s post-credits scene.
That said, Justice League makes very few references to Lex, so this paper provides further insight into how Earth’s citizens responded to the mysterious crisis in Russia.
Lex Luthor technically did call Steppenwolf in Batman v Superman: Dawn of Justice, which eventually paved the way for Darkseid’s uncle to show up in his quest for the Mother Boxes.