Two things have stood out to me as I’ve considered this question. The first is the Jewish view of what happens to the soul after death; the second is the literary evidence in the epistles and gospels for the evolution of the doctrine of the resurrection.
The Jews believed that when a person died their soul went down to Sheol, the place of the dead. This was not a place of eternal judgment (unlike hell) but a place where one loses all agency. Psalm 115:16-18 is a good example: “The highest heavens belong to the Lord, but the earth he has given to humankind. It is not the dead who praise the Lord, those who go down to the place of silence.”
I think it’s quite reasonable to say that the earliest understanding of Jesus’ resurrection was that God did not leave him in Sheol, but exalted him to heaven. This is in line with Paul’s very clear teaching that the resurrection is spiritual, not physical.
What I really find interesting is reading the New Testament in chronological order paying particular attention to the doctrine of the resurrection. You will quickly see that the earliest writings put very little emphasis on the resurrection. The earliest Gospel (Mark) barely mentions it. When it is mentioned in the Gospel there is good evidence that the phenomenon is something other than physical as the disciples don’t recognize him, he walks through walls, suddenly disappears, etc. The main focus of the earliest writings was not the resurrection, but the crucifixion and imminent (and I mean VERY imminent) return of Christ.
That being said, there are clear places in the Bible that seem to talk about Jesus’ physical resurrection. There isn’t much need to discuss the empty tomb and the conspiracy to explain it away if there is only a physical resurrection. So were these people lying? I don’t think so, but I do think they (eventually) remembered it wrong. After years of talking about Jesus spiritual resurrection, it’s quite possible the memory evolved into the idea of a physical resurrection. That would explain why they told themselves they didn’t quite recognize him at certain times, and some of the other strange bits.
I know that almost any devout Christian reading that last paragraph will interpret it as a weak attempt to explain away the heart of the gospel message. I would have had the same opinion myself not long ago. Before you dismiss it though, I would recommend doing some research into human memory and how malleable it is. For a quick and fascinating summary, listen to Malcom Gladwell’s podcast “Revisionist History.” Episode 3 (A Polite Word for Liar) and 4 (Free Brian Williams) of season 3 will be particularly relevant to this discussion.