There are aspects to the resurrection story that seem unnecessary but make perfect sense if you consider them as patches to shore up the lie of Jesus' resurrection.
(1) Why did there have to be angels present at Jesus' resurrection? There is no other resurrection account in the bible that mentions the involvement of angels.
Possible explanation: Jesus' disciples really did steal Jesus' body from the tomb. Two or three of them ambushed and knocked/drugged unconscious the guards on the scene before stealing the body. Later when they awaken and find the body missing they relate how they were ambushed and come to the conclusion that this was the work of his disciples. The disciples deny this and claim he was resurrected, but others testify to the fact that the guards were found unconscious, suggesting that foul play really did occur. The disciple explain the unconsciousness by saying there were angels present at the resurrection and the guards were overcome to the point of unconsciousness, by their glory. They further claim that the guards were paid to lie by saying the body was stolen, to hide the fact of the resurrection that they had witnessed.
(2) Why would gospel accounts claim that Jesus' disciples were kept from recognizing the resurrected Jesus? There is no other resurrection account where the resurrected were unrecognizable.
Possible explanation: The "resurrected Jesus" didn't really exist and so no one saw him walking about. How could the disciples reconcile this inconvenient fact with the claim that he was resurrected? Simple: claim that God miraculously kept him from being recognized, so many saw him but didn't know at the time that it was him. This is a very clever bit of deception because it would allow the disciples to convince gullible people who wanted to believe it, that they were actually personal eyewitnesses of the resurrected Jesus but they didn't know it at the time. Imagine: respected leaders in your cult tell you that you saw and spoke to the resurrected Jesus but you are perplexed because you recall no such thing. They explain to you that the reason you don't remember is that you didn't recognize him because his appearance was miraculously masked. "Remember that stranger you spoke to on the road to Emmaus - that was the resurrected Jesus in disguise! You saw and spoke with him!!" I bet more than a few disciples would prefer to believe this lie that puts them in privileged position. There may even have been a Jesus imposter pretending to be the resurrected Jesus.
In other words, some of the unnecessary details in the resurrection narrative could actually be patches invented to cover inconsistencies in reality that disprove the resurrection claim. Why would the disciples have engaged in these deceptions to convince others that Jesus had been resurrected? For the "greater good" of the movement - so that the movement didn't die out through the great grief and disappointment that came with Jesus' death.