You also asked why would
the blessed hope (Rapture) protect some Christians and not
others.
There are some people who call themselves
Christians and talk the talk, but do not walk the walk.
The Rapture is not going to protect those left behind who
are in a state of sin which they haven't repented of.
They are not ready to go to heaven with the Lord Jesus, and
need more time to repent of their sins so they are left
behind to be given more time to repent and to confess their
sins and receive forgiveness. The Lord doesn't bless
those who are workers of iniquity and sin. The
overcomer of sin is blessed.