3. When the world did not end, the inadequacies of Mark's narrative became obvious and a more detailed explanation became necessary, answering questions about his origins, his teaching, his relationship to the Law, and especially why he was rejected by the Jewish authorities and died at the hands of Romans. If we read the passion and resurrection narratives of the Synoptics side-by-side, we see that the passion accounts don't different much, while the resurrection accounts appear to be written by people seeking answers and struggling to understand what they're describing. 

4. By the time Luke-Acts is written, the author -- also a companion of Paul? -- sees the need for an account that weaves the Jesus story into the mission and he composes his two-book sequence with Paul as a Christ figure. In my view, the existence of three Synoptic accounts derives not from multi-cultural origins, but from a need to answer questions posed by people who demanded answers. (out of space again....)