[Quester]

Do you have any evidence that this one infiltrator had a lasting effect on the development of Christianity ?

There is evidence in the bible of rebellion within one of the early churches, a revolt against John and apparently the authority he had:

3 John 1:9 I wrote something to the church; but Diotrephes, who loves to be first among them, does not accept what we say.

10 For this reason, if I come, I will call attention to his deeds which he does, unjustly accusing us with wicked words; and not satisfied with this, he himself does not receive the brethren, either, and he forbids those who desire to do so and puts them out of the church.

It's not a stretch to imagine that the church Diotrephes belonged to became corrupt because they rejected the authority of John. Whether Simon Magus had direct influence is unknown, but the problem of corruption began to occur early.

Yes ... individual churches had issues from the very beginning ... Corinth, Galatia, Thessalonica, Ephesus, etc ... even as they do today.

Church leadership has had to consistently deal with these issues.

Note Jesus' letters to the churches cited in Revelation.

[DouglasKC]

Yes ... individual churches had issues from the very beginning ... Corinth, Galatia, Thessalonica, Ephesus, etc ... even as they do today.
Church leadership has had to consistently deal with these issues.
Note Jesus' letters to the churches cited in Revelation.

Very true. I find it telling that so much corruption was evident even in biblical times.