::My understaning has been that as late as the 70s and 80s, Christianity was viewed (even by Christians) as Jewish sect.  The writer of the Gospel of Matthew, in fact, whomever it was, was at least in part trying to claim that Christianity was the true, legitimate Jewish faith. That Gospel dates to the 70s or 80s, scholars believe.  It wasn't until the council at Jamnia/Javneh circa 95 CE that the big split occurred.  At least that's how I've understood it, for what it's worth.