The Holy Spirit was sent to us to teach and guide us in our walk with Christ. He is the one that restrains.
Paul says he is taken away. No need for him here as we are taken also.
Paul also said we are not subject to wrath so why would God leave his children to suffer???
IMO those that are killed because they would not bow enter into the millennium by there own blood which is why perhaps Satan returns to tempt men away again.
It may be a weak attempt to explain the martyrs but perhaps there is someone who can give a more detailed answer.
Paul doesn't state who the restrainer is. In 2 Thessalonians 2 he assures the church that the day of the Lord has not come because
false teachers are spreading lies about his second coming, (they still are), He goes on to say this
Let no one deceive you in any way for that day will not come unless the rebellion comes first
and the man of lawlessness is revealed, the son of perdition who opposes and exalts himself
against every so called god or object of worship so he takes his seat in the temple of God proclaiming
himself to be God. Do you not remember that when I was still with you I told you. And you know what
is restraining him now so that he will be revealed in his time. For the mystery of lawlessness is already
at work, only he who now restrains it will do so until he is out of the way. And then the lawless one
will be revealed and the Lord Jesus will slay him with the breath of his mouth and destroy him by his
appearing and his coming.
2 Thessalonians 2: 3-8
In this passage Paul doesn't state who the restrainer is. It is assumed to be the Holy Spirit but could really
be the Archangel Michael who according to Jewish belief is the protector of Israel. Its Michael who is sent to Daniel
and who casts Satan and his host out of Heaven.
Gods wrath is poured out on the earth at Christ second coming when the saints are raptured and the Antichrist
is destroyed with the breath of his mouth. The righteous dead are resurrected and those alive will go with them
to meet the Lord in the air as he descends to the mount of olives.