I was just wondering how the Assemblies of God, Baptists, etc, came to their current teaching on this.
Any input appreciated...
Most modern Baptists and Pentecostals, etc, are descended from austere and pious sects that emerged before and during the Reformation. There were the Waldenses, and the Anabaptists, which we still have with us today.
During the reformation, they at first had the same understanding as you express. However, after some of them were executed for bigamy, since the authorities at the time did not recognize divorce, they decided that they should eschew divorce for the sake of their testimony. Consequently, they would never allow any divorce-remarried to occupy leadership positions in the church, where they were highly visible.
To this day, the Anabaptists will consider you as lost and going to Hell if you are divorce-remarried, unless you and your current spouse separate and reconciliation with the former spouse is actively pursued, regardless of how little chance there is for same.
31 “It has been said, ‘Anyone who divorces his wife must give her a certificate of divorce.’ 32 But I tell you that anyone who divorces his wife, except for marital unfaithfulness, causes her to become an adulteress, and anyone who marries the divorced woman commits adultery.
Matthew 5 (NIV)
It seems to be a twist from what Jesus actually said.