I. How is somebody in Greece going to know intimate details of Jesus' ministry if they were living 60 years later and a thousand miles away from Jerusalem?
Someone well informed with access to good sources would known those details……………….. how do you know that Germany Invaded Poland in 1939? (this is something that happened 70 years ago and in another country)
Here's a question for you: how did the author of Luke's gospel know that an angel appeared to Jesus in Gethsemane to comfort him? The apostles were some place else asleep.
I don’t know
Maybe
1 Jesus told someone before he died
2 Maybe he told someone after he died (while being resurrected)
3 Maybe though divine revelation
4 Maybe Luke lied
5 Maybe Luke made an honest mistake
The thing is that Christianity could still be true regardless of which alternative you pick.
The truth of the resurrection is grounded on 5 Facts that most scholars accept
1 The existence of God is at least possible
2 Jesus died on the cross
3 Jesus was buried
4 The tomb was found empty
5 Early Christians had experiences that they interpreted as having seen the risen Jesus
All of these 5 facts are accepted by most scholars, so your alternatives are
1 ether deny some of these facts and go against the consensus of scholars
2 find a better explanation for these facts