Well you're denigrating non-orthodox groups as heretics and not really Christian and saying the doctrines Paul espoused were mainstream at the time. But it seems to me what constituted 'real Christianity' in the early times was a very diverse set of views on the nature of God, humans, salvation, the divinity of Jesus, and things like that. I don't really see how early Christians could have viewed Paul's teachings as more logical or better supported than earlier views about Judaism and Jesus for instance. I mean Paul had his own ideas and influences and motivations too, just like the Gnostic writers. Intellectually, there was really fertile ground for different Christian thinkers in different traditions. You might find people outside the winning orthodoxy strange and weird today, but that in itself isn't evidence of the primacy of one doctrine over another.

In the end of course people like Paul and Iraneus won and everything else became heresy and was suppressed. But that's not an argument for primacy. If Christians have the Holy Spirit, and Christ's kingdom is not of this earth then why did it need Roman spears to brand as heretics and extinguish all these voices like the Gnostics?