Your problem with understanding and appreciating the situation with Simon the Magician is because of two things:
- You are not taking scripture at its face value.
- You are superimposing your doctrine on the text.
Jesus says this about belief and baptism:
“He who believes and is baptized will be saved; but he who does not believe will be condemned.”[Mark 16:16]
In Acts I:13 we learn this about Simon the Magician:
“Even **Simon himself believed, and after being baptized **he continued with Philip. And seeing signs and great miracles performed, he was amazed.”
Simon is not called a false believer or a false professor. Scripture says that he was a believer and that he was baptized. He meets the criteria stated by Jesus. To suggest that he was not regenerated is to superimpose your doctrines on the scriptures rather than letting the scriptures explain the truth to you.
The Holy Spirit comes to us in baptism, but the Holy Spirit can also come upon us in other ways and at other times. We see this in both the OT and the NT. An example in the NT is when Peter who had already received the Holy Spirit at Pentecost receives the Holy Spirit again in Acts 4. In that passage we are told that Peter and John are arrested and brought before the high priest and the elders. When questioned by them Peter is ready to respond when scripture says, “Then Peter, filled with the Holy Spirit, said to them,…”[Acts 4:8] Receiving the Holy Spirit on an occasion separate from baptism does not mean that we do not receive the Holy Spirit at baptism. One does not preclude the other.
What happened to Simon is that he was tempted and he had a lust for the power that comes through the laying on of hands. He is even willing to pay for that power with money, and it is then, and only then, that he is rebuked by Peter. Peter’s warning to Simon frightens him. He realizes that his sin may have eternal consequences and asks that Peter pray that none of this would happen to him.
Justification and regeneration can be lost. There is nothing in scripture that indicates that a believer cannot leave the household of God. It is by the gift of grace that we have faith and are freed from committing sin. We can reject that gift and leave the household. We can leave the household to live a life of sin and dissipation in the flesh.