I don't really see the issue here. Obviously it doesn't make sense to us if we view this through an atheistic lens, but theologically speaking it seems the idea is that Moses, etc. were basically on God's right track (so to speak) whereas Judaism (as an entity separate from Christianity and this track) developed more as an aberration due to the denial of Jesus as Christ. Thus the good guys continued on recognizing that Christ is the savior whereas the Jews were stubborn and refused, progressing from that point on into a faith the prophets, had they still lived, would have opposed as God would presumably have instructed them to do since the same God that was said to inform them was the same God who gave the world baby Jesus.
Of course this can also produce anti-semitic undertones.
It's worth noting that according to Islam every single Prophet (including Adam, considered the first) were Muslims. They use a similar line of reasoning as this Christian guy apparently does.
I mean I could be wrong and maybe this guy actually does think that Moses was around in Jesus' time or came after or something, but I'm pretty sure he adheres to what I just said.