Christianity is based in history. Luke in his gospel appeals to eyewitness testimony (Luke 1:1-4), as does Peter in his epistle (2 Peter 1:16). Other NT writers do the same. A person’s response to historical events—the incarnation and the resurrection, for example—are decisive to their salvation.
Did the early church invent Jesus and His sayings to fit certain issues they dealt with? It is unlikely, since much of what they faced isn’t addressed in the gospels, e.g. speaking in tongues, circumcision of Gentiles, the mission to the Gentiles.
Inventing the character of Jesus would take another Jesus
In other words, it would be a miracle. Even radical atheists and agnostics have taken this view. Following are some quotations from people who were anything but friends of Christianity that Dr Lindsley cites, along with the sources I dug up:
“It takes a Newton to forge a Newton. What man could have fabricated a Jesus? None but a Jesus.”
–Theodore Parker [Source]
“It is of no use to say that Christ as exhibited in the gospels is not historical, and that we know not how much of what is admirable has been superadded by the tradition of his followers. … But who among his disciples, or among their proselytes, was capable of inventing the sayings ascribed to Jesus, or of imagining the life and character revealed in the Gospels? Certainly not the fishermen of Galilee; as certainly not St. Paul, whose character and idiosyncrasies were of a totally different sort; still less the early Christian writers, in whom nothing is more evident than that the good which was in them was all derived, as they always professed that it was derived, from the higher source.”
–John Stuart Mill [Source]
“It is more inconceivable that several men should have united to forge the Gospel than that a single person should have furnished the subject of it. The Gospel has marks of truth so great, so striking, so perfectly inimitable, that the inventor of it would be more astonishing than the hero.”
–Jean Jacques Rousseau [Source, page 9]
“Jesus himself, as he appears in the Gospels, and for the very reason that he is so manifestly above the heads of his reporters there, is, in the jargon of modern philosophy, an absolute; we cannot explain him, cannot get behind him and above him, cannot command him.”
–Matthew Arnold [Source, para. 17]
Part 2: Aspects of Jesus’ teaching and personality that would have been difficult to replicate.