This request to the Father to forgive them and this verse below may be grounds for why no one should blame the Jews for crucifying Him.
John 10: 18 No man taketh it from me, but I lay it down of myself. I have power to lay it down, and I have power to take it again. This commandment have I received of my Father.
Matthew 20: 28 Even as the Son of man came not to be ministered unto, but to minister, and to give his life a ransom for many.
One may discern that in Acts 2, that these may be the very Jews that were in the mob that had chosen to crucify Jesus in unbelief.
Acts 2:14 But Peter, standing up with the eleven, lifted up his voice, and said unto them, Ye men of Judaea, and all ye that dwell at Jerusalem, be this known unto you, and hearken to my words: 15 For these are not drunken, as ye suppose, seeing it is but the third hour of the day. 16 But this is that which was spoken by the prophet Joel; 17 And it shall come to pass in the last days, saith God, I will pour out of my Spirit upon all flesh: and your sons and your daughters shall prophesy, and your young men shall see visions, and your old men shall dream dreams: 18 And on my servants and on my handmaidens I will pour out in those days of my Spirit; and they shall prophesy: 19 And I will shew wonders in heaven above, and signs in the earth beneath; blood, and fire, and vapour of smoke: 20 The sun shall be turned into darkness, and the moon into blood, before the great and notable day of the Lord come:
21 And it shall come to pass, that whosoever shall call on the name of the Lord shall be saved. 22 Ye men of Israel, hear these words; Jesus of Nazareth, a man approved of God among you by miracles and wonders and signs, which God did by him in the midst of you, as ye yourselves also know:
23 Him, being delivered by the determinate counsel and foreknowledge of God, ye have taken, and by wicked hands have crucified and slain: 24 Whom God hath raised up, having loosed the pains of death: because it was not possible that he should be holden of it.
32 This Jesus hath God raised up, whereof we all are witnesses. 33 Therefore being by the right hand of God exalted, and having received of the Father the promise of the Holy Ghost, he hath shed forth this, which ye now see and hear. 34 For David is not ascended into the heavens: but he saith himself, The Lord said unto my Lord, Sit thou on my right hand, 35 Until I make thy foes thy footstool.
36 Therefore let all the house of Israel know assuredly, that God hath made the same Jesus, whom ye have crucified, both Lord and Christ. 37 Now when they heard this, they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do? 38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. 39 For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call.
Since they cannot come to the Son unless the Father has drawn them to reveal His Son to them so they can believe in him and be saved, I can see why Jesus asking the Father for forgiveness may be necessary so He would do that.
John 6: 44 No man can come to me, except the Father which hath sent me draw him: and I will raise him up at the last day.
Matthew 11:25 At that time Jesus answered and said, I thank thee, O Father, Lord of heaven and earth, because thou hast hid these things from the wise and prudent, and hast revealed them unto babes. 26 Even so, Father: for so it seemed good in thy sight. 27 All things are delivered unto me of my Father: and no man knoweth the Son, but the Father; neither knoweth any man the Father, save the Son, and he to whomsoever the Son will reveal him.
John 6:37 All that the Father giveth me shall come to me; and him that cometh to me I will in no wise cast out. 38 For I came down from heaven, not to do mine own will, but the will of him that sent me. 39 And this is the Father's will which hath sent me, that of all which he hath given me I should lose nothing, but should raise it up again at the last day. 40 And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day.
It may also be necessary for Jesus to ask that of the Father to set the example for when we suffer grief wrongfully.
1 Peter 2:19 For this is thankworthy, if a man for conscience toward God endure grief, suffering wrongfully. 20 For what glory is it, if, when ye be buffeted for your faults, ye shall take it patiently? but if, when ye do well, and suffer for it, ye take it patiently, this is acceptable with God.
21 For even hereunto were ye called: because Christ also suffered for us, leaving us an example, that ye should follow his steps: 22 Who did no sin, neither was guile found in his mouth: 23 Who, when he was reviled, reviled not again; when he suffered, he threatened not; but committed himself to him that judgeth righteously: 24 Who his own self bare our sins in his own body on the tree, that we, being dead to sins, should live unto righteousness: by whose stripes ye were healed. 25 For ye were as sheep going astray; but are now returned unto the Shepherd and Bishop of your souls.
There is more than one way to apply what Jesus has done in asking the Father to forgive the Jews at His crucifixion, but according to these scriptures, it sure looks like the Father did forgive them.