For godly grief produces a repentance that leads to salvation without regret, whereas worldly grief produces death
(2 Cor 7:10)
i believe what Judas experienced was worldly sorrow. he was terrified in his conscience over what he had done, but it wasn't penitent terror. you see the same thing in King Saul (you can read his story in 1 Samuel
). when confronted with his sin, Saul shifted the blame to other people, never seeking God for forgiveness in repentance.
contrast that with King David, who acknowledged his sin to the Lord and sought forgiveness. (Ps 51)
one king exhibited worldly sorrow; the other Godly sorrow.
Judas was seeking relief from his conscience, yet not forgiveness from God. hope that makes sense.