And they had No idea to what extant Paul had deviated from the message that they preach of Jesus Christ.
Pistolpete, let's review the Facts:
1. We know Paul spent 15 days in Peter's house. James - Jesus' brother was also there for the discussions as well.
2. 14 years later, Paul comes to Jerusalem where he updates the other apostles on what he has been teaching the Gentiles and they "add nothing to him" and all extend the right hand of fellowship.
3. Then after that, Peter writes this:
2 Pet. 3: 15 And account that the longsuffering of our Lord is salvation; even as our beloved brother Paul also according to the wisdom given unto him hath written unto you; As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.
17 Ye therefore, beloved, seeing ye know these things before, beware lest ye also, being led away with the error of the wicked, fall from your own stedfastness.
Paul was a first rate philosopher. Just read his writings and you will see that. Peter defends Paul when some were taking what Paul wrote and were twisting into it into something that it wasn't.... to their own destruction. He warned about being "led away" by the error of the wicked - presumably those that were twisting Paul's words. Peter calls Paul a "beloved brother".
Peter also wrote on the same topics as Paul, like the Substitutionary Atonement :
Who his own self bare our sins in his own body on the tree, that we, being dead to sins, should live unto righteousness: by whose stripes ye were healed. 1 Peter 2: 24
1 Pet. 3: 18 For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened [made alive] by the Spirit:
The Watchtower rejects the Substitutionary Atonement taught by Peter and Paul and tries to claim that Jesus paid back what Adam lost! Not much has changed.
The facts above do not support your proposed dual gospel. In Galatians 1: 8-9 Paul announces a double curse for anyone who preaches a different gospel than what he and the other believers preached.
Substitutionary Atonement and Vicarious death have been bedrock Christian doctrine since the beginning unto this very day. Thousands of years of vicarious animal sacrifice in the OT prepared people for not only the concept of vicarious punishment, but also for the appearance of the Lamb of God who died in our place.
It is an amazingly unified message that spans scores of writers, over more than a dozen centuries.