When you say it's well established, what you are really saying is that skeptic and atheist scholars assume that the stories in the gospels are not true and inspired by earlier stories.
They look to be inspired by earlier stories. The OT, Paul, Greek stories,
For example, Greek stories -
Odyssey 9 and 10 /Mark 5:1-20
O - Odysseus and his crew sailed to the land of the Cyclopes.
M - Jesus and his disciples sailed to the region of the Gerasenes.
O - On the mountains of the Cyclopes innumerable goats grazed
M - On the mountain a large herd of swine grazed
O - Odysseus and his crew disembarked.
M - Jesus and his disciples disembarked
O - Polyphemus usually was depicted nude.
M - The Demoniac was nude.
O - Circe recognized Odysseus and asked him not to harm her. The giant asked if Odysseus intended to harm him.
M - The demoniac recognized Jesus and asked him not to harm him
O - The giant asked Odysseus his name.
M - Jesus asked the demoniac his name.
O - Odysseus answered “nobody is my name”
M - The demoniac answered “Legion is my name”
O - Odysseus subdued the giant with violence and trickeryM - Jesus subdued about 2000 demons with divine power and sent them into the swine and then drove the swine into the lake.
M - Jesus subdued about 2000 demons with divine power and sent them into the swine and then drove the swine into the lake.
O - Polyphemus the Shepard called out to his neighbors.
M - The swineherds called on their neighbors.
O - The Cyclopes came to the site asking about Polyphemus’s stolen sheep
M - The Gerasenes came to the site to find out about their swine.
O - Odysseus and crew embarked.
M - Jesus and his disciples embarked.
O - Odysseus told the giant to proclaim that he had blinded him.
M - Jesus told the healed demoniac to proclaim what God had done for him.
O - The giant asked Odysseus, now aboard ship, to come back.
M - The demoniac asked Jesus, now aboard ship, if he could be with him.
O - Odysseus refused the request.
M - Jesus refused the request
O - Odysseus and crew sailed away.
M - Jesus and disciples sailed away.
O - Odysseus awoke during a tempest in the episode immediately following the story of the Cyclops.
M - Jesus awoke during a tempest and calmed the wind and sea just before exorcising the demoniac.
Mark/Odyssey 19
1)Odyssey - Telemachus was amazed at the great light that shone on the walls of his house. Odysseus interpreted the light as the presence of Athena.
Mark - One of Jesus’s disciples was amazed at the great buildings in the Jerusalem temple, Jesus predicted that these buildings will be destroyed.
2) Odyssey- Odysseus went to Penelope and sat
Mark - Jesus went to the Mount of Olives and sat.
3) Odyssey - Penelope, in private, questioned her husband in disguise.
Mark - Four of the disciples, in private, asked him about the destruction of the temple.
4) Odyssey - Odysseus gave her signs that he had seen her husband and that he would soon return.
Mark - Jesus gave the sign when he would return.
5) Odyssey - That very day Odysseus was consulting the oak sacred to Zeus at Dodona.
Mark - The disciples should consult the fig tree.
6)Odyssey - He is near
Mark - He is near
7)Odyssey - ”..all these things will come to pass”
Mark - “..until all these things take place.”
8) Odyssey - No one in Ithaca knew if or when Odysseus would return
Mark - It is like a man on a trip…Keep watch, because you do not know when the lord of the house is coming
9) Odyssey - The suitors were prepared to kill Telemachus and Odysseus.
Mark - The chili priests and scribes were seeking some deceitful way to arrest and kill him
10)Odyssey - The suitors feared harm from the people of Ithaca.
Mark - The authorities feared a popular uprising
11)Odyssey - After giving his prophecies to Penelope, Odysseus, disguised as a beggar, sat by himself.
Mark - After giving these prophecies to four disciples, Jesus sat at table in the humble home of a leper.
12) Odyssey - Eurycleia entered with a bowl of water to wash his feet; later she anointed him generously with oil.
Mark - A woman entered with an expensive stone jar of ointment and poured the contents on Jesus’s head.
13)Odyssey - When she recognized her master, she dropped his leg into the brass vessel, spilling the water.
Mark - She broke the jar to release the oil.
14)Odyssey - She alone recognized her king.
Mark - She alone recognized Jesus soon would die.
15) Odyssey - Melantho had objected to Penlope’s generosity to the poor, not showing hospitality to Odysseus the beggar was performing a monstrous act
Mark - People objected that the ointment could have been sold and the money given to the poor. Jesus told them she had performed a beautiful act.
16)Odyssey - Eurycleia means “renowned far and wide” Penelope told her that one who welcomes strangers will have fame far and wide.
Mark - Jesus said, “wherever the good news is proclaimed throughout the world, what this woman has done also will be spoken of in her memory”.
17)Odyssey - Odysseus and Eurycleia discussed the disloyalty of some of the slaves
Mark - Then Judas Iscariot…went to the chief priests for the purpose of betraying him.
Greek school of writing, literary imitation or
Mimesis and syncresis.
Jesus is like Odysseus but better. He’s like Hector in his death but he comes back and so on.
From PhD Dennis McDonald