There is much that can be said, I haven’t come to a conclusion yet, But a few scriodo pop out.
We see that this sin is regarding the 'third part' of the Trinity, the Holy Spirit of God. It is not stated to be one who blasphemes God nor His Christ, but only His Holy Spirit (but they are One

And that the 'assault' on that Holy Spirit is the unforgivable sin:
We see that it is impossible to find forgiveness for one who has committed this sin — there is no way back for them, no repentance available to them. We also see a little deeper into what the nature of this unforgivable sin is. We see that only believers can commit this sin. We also see it associated with the "falling away," which brings our minds to "...for that day
[Second Advent] shall not come, except there come a falling away first...." (II Th 2:3):
Heb 6:4-6
4 For
it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost,
5 And have tasted the good word of God, and the powers of the world to come,
6
If they shall fall away, to renew them again unto repentance [no forgiveness]; seeing they crucify to themselves the
Son of God[Jesus Christ AFTER He ascended] afresh, and put him to an open shame. (KJV)
We see the unhappy state of one who commits this unforgivable sin:
I Jn 5:16-17
16 If any man see his brother sin a sin which is not unto death, he shall ask, and he shall give him life for them that sin not unto death.
There is a sin unto death: I do not say that he shall pray for it.
17 All unrighteousness is sin: and there is a sin not unto death. (KJV)
Ecclesiastes 8
16 I tried to understand all that happens on earth. I saw how busy people are, working day and night and hardly ever sleeping. 17 I also saw all that God has done. Nobody can understand what God does here on earth. No matter how hard people try to understand it, they cannot. Even if wise people say they understand, they cannot; no one can really understand it.