William Lane Craig explains that the Gospels were likely written at nearly the same time as Paul’s epistles (1 Corinthians 15 was penned in 55 AD). The Book of Acts occurred in mid AD 60s (before James died and temple was destroyed in 70 AD). Luke was written before Acts by the same author around 57 AD. Mark’s Gospel was used by Luke, putting Mark even earlier.
The Gospels were spread orally before they were written. But, because all those writing the Gospels were so closely connected to the events (not 30 years had passed since Jesus’ death), the authors were not writing oral traditions. Instead, the 4 Gospel writers were doing oral histories — actually asking the many still-living eyewitnesses what had happened. 2 writers were apostles themselves, Matthew and John) and had witnessed many things first hand.
Jewish children were taught at home, school, and in the synagogue to memorize massive amounts of faithful information. Memorization and faithful transmission was prioritized. Jesus’ disciples surely utilized this skill. No legend. No mythology. No telephone game.
Jeff organized scholarship to present a LDS perspective: