Was Jesus of Nazareth a religious loon?

[Jehanne]

For centuries, it was widely believed among scholars that the Gospel of Matthew was the first Gospel to have been written:
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Of course, one must wonder if the Angel really did visit Mary, the supposed mother of Jesus, how she could have ever drawn the conclusion that her son had "lost it"??

The tradition that Mark recorded is almost certainly authentic, in that it is early, and per the criterion of "embarrassment", it is likely historical.  It would also explain why Jesus, after going to Jerusalem, "stood out", by being an audacious, eccentric preacher, which is why both the Jewish and Roman authorities noticed him, and ultimately, had him arrested and then executed.

There's a number of points here.

Firstly the priority of Mark is far from settled, but let's use it as an assumption for now.

Secondly, Mark 3:21 is almost certainly authentic- it is highly unlikely the Early Church would have invented it as you say.

Thirdly, the apparent conflict with Luke's angelic visit only appears substantial this side of the resurrection. Before then, the whole Jesus-as-God thing was unthinkable. Mary's message was by and large consistent with normal C1 revolutionary Judaism similar to Bar Kokhba and Joseph had something about saving from sins (long story short, the same thing as a successful military revolution). So Mary probably saw Jesus' increasingly unusual and freaky Kingdom pronouncements as the wrong road to take, and wanted to implement some motherly intervention.

Finally, it is clear that that the relationship between Jesus and His family was notable for a lot of tension and disbelief (also see Mark 3:31-35 parr, John 7:5). It is therefore all the more startling to find Jesus brother James highlighted as a prominent 'drop by and ask him about it' witness in 1 Cor 15:7, and being given the leadership of the Jerusalem church- with other family members following in his steps.

The obvious explanation would be that James actually was a witness to the resurrection, I suppose.

Mark, of course, does not have an Virgin Birth narrative, and Matthew & Luke offer varying versions; Paul seems either ignorant and/or disinterested entirely.  As for John, it's irrelevant, as for him and his community, Jesus was preexistent to his birth.

I doubt, in the extreme, that either Matthew or Luke's account contain any real history, other than the fact (probably historical) that Jesus was born in Nazareth.  We have the extreme tale of King Herod's "massacre of the innocents" not recorded by any contemporary pagan or Jewish historians, and as such, most modern scholars regard it as being myth and/or fable, which makes the whole of Matthew's account, written nearly a century after the supposed events completely suspect.