What about Jesus of the Gospels does Paul seem unfamilare with ?
Well, Paul doesn't seem to actually know who put Jesus to death (1 Cor 2:8) Paul doesn't seem familiar with Jesus instruction on how to pray. (Romans 8:26) Paul doesn't seem familiar with Jesus' very specific instruction to baptize (1 Cor 1:17)
Paul makes no mention of the virgin birth, Jesus' parents, Jesus' miracles, Jesus birthplace, Jesus Roman trial, or the empty tomb.
Time after time, Paul relies on his own long-winded reasoning when it would have made more sense to quote Jesus. If the Gospel accounts are factual, Jesus had already said these things more succinctly and with more authority:
Romans 2:1-16 vs. Matthew 7:1
Romans 12:14-17 vs. Matthew 5:44
Romans 13:1-7 vs. Mark 12:17
1 Thessalonians 4:9 vs. John 15:17
We could observe that Paul is essentially in agreement with Jesus in these verses, but that's not the point. Paul is either not giving credit where credit is due or he's ignorant that Jesus had already said these things, or as some source critics conclude, Paul is the actual author of much of Christian theology.