Why does lex luthor often team up with superman against greater threats?

Lex Luthor's relationship with Superman is defined by being his archenemy, yet character traits like pragmatism and calculation lead to temporary alliances in certain storylines. As an ordinary human without superpowers, Luthor relies on intellect, wealth, and influence rather than physical strength. His primary motivation often centers on preventing Superman from becoming a threat to humanity or eliminating him entirely. However, when facing existential threats like Doomsday, Darkseid, or cosmic-level dangers, Luthor's strategic mind recognizes that Superman's abilities may be necessary to defeat these greater evils. This creates temporary partnerships where enemies acknowledge that their shared survival or agenda takes precedence over their conflict. In many DC Comics storylines, including films like 'Batman v Superman: Dawn of Justice,' Luthor manipulates situations to use Superman's power when it serves his goals, demonstrating that his actions are driven by practical necessity rather than genuine alliance. This behavior reflects his character's complex nature as both villain and reluctant pragmatist in a universe where the greatest threats often demand unlikely partnerships.