More likely these are they who repent and receive Salvation after the rapture. Then they are killed for their faith, as they refuse to worship the Beast.
Some of the pre trib people believe after rapture Holy Spirit not on earth anymore.
How people believe and willing to die without the helping of the Holy Spirit ?
John 15
4 Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me.
When Jesus on earth, Jesus teach and helping people to understand about salvation. Then Jesus go to the Father, He send Holy Spirit to help people to bear the fruit. Jesus say branch can not bear fruit of II self.
What is fruit of the Holy Spirit? It is love
Die for Jesus is big love, not take the mark and die is love for Jesus and it is the fruit of the Holy Spirit.
Jesus say branch cannot bear fruit of itself, mean impossible for a man willing to die for Jesus without the help of the Holy Spirit.
Do the theory after rapture no Holy Spirit on earth and the believer that not take the mark is new believer after rapture is not biblical.
This theory mean, it is possible for branch to bear fruit without the help of Holy Spirit.
It mean this theory do not believe in Jesus teaching.