" What didn't the rulers understand? God's wisdom in His plan of redemption.

How do we know that that's what they didn't understand?1 Cor 2:8: "for if they had understood it, they would not have crucified the Lord of glory..." The "rulers of this age" are powers and principalities, Satan and his minions—the religious stooges he put up to crucifying Jesus. Those powers—Satan, et al—would never have crucified Jesus if they had known that in doing so they would enable Him through His atoning death to set His elect free from sin's bondage!