The ‘gilding the lily’ idea assumes that the teaching of the crucifixion and resurrection made the gospel more appealing: it didn’t.
Paul, writing 1 Corinthians in about AD 55, comments: ‘Jews demand miraculous signs and Greeks look for wisdom, but we preach Christ crucified: a stumbling-block to Jews and foolishness to Gentiles,’ (1 Cor 1:22-3). So the considered opinion of Paul (who is supposed to have been one of the chief proponents of such a strategy) is that it was a bad idea. This can be clearly seen in the reaction of the crowd to Paul’s message in Athens. As long as he spoke in philosophical terms, they listened; but as soon as he mentioned the resurrection, they began to mock (Acts 17:32).
In fact, gnosticism had far more appeal to Greek thinkers: yet the church strenuously opposed this teaching when attempts were made to introduce it.
Making Jesus out to be the only true Son of the only true God wasn’t a smart marketing move either. This brought them into direct conflict with both the Romans (who regarded any who would not worship Caesar as atheists) and the Jews (who regarded it as blasphemy).
Similarly, to the Jews the idea of a crucified Messiah was a serious obstacle, as they were convinced Messiah would never die (Jesus would have had a far better chance as a murdered prophet – there were plenty of those!). A similar problem applied to Greek culture as well: lowliness was a highly despised attribute – yet Jesus exemplified it as the one who had come to die for all the filth of this world. And portraying the Roman governor as the one who, by his weakness, made the whole travesty of justice possible wasn’t exactly going to endear them to the Romans either!
Yet, far from back-pedalling or softening the message of the crucifixion, Paul declares in his second letter to the Corinthians, written about a year after the first: ‘And I, brethren, when I came to you, came not with excellency of speech or of wisdom, declaring to you the testimony of God. For I determined not to know any thing among you, save Jesus Christ, and him crucified.’ (1 Cor 2:1).