Jesus did all that he could. He died for sinners. He prayed for sinners. Now we who are sinners must come to him. Ignorance caused Jesus' murderers to fail to discern the fact that they were crucifying the Lord of Glory.
Man remains, for the most part, spiritually ignorant.
There are those who have heard the truth and can believe it if they want to believe it. Their unbelief is a wilful refusal on their part to accept the truth. Jesus was not seeking to excuse his enemies' sin because of their ignorance. These men knew that what they were doing was wrong. They were murdering an innocent man.