Was Jesus of Nazareth a religious loon?

[Vicki Q]

Okay, you're a literalist

Not at all, and focussing on my last sentence has rather sent you off in the wrong direction, I'm afraid.
To repeat and hopefully clarify- there are strong arguments which say the Matthew pre-resurrection return from the dead didn't happen, and strong arguments which say that it did. I'd go non liquet.
If you're planning on discussing this further, please review the arguments and you'll no doubt see why the alien reference fails.

But, why did the pagan philosopher Seneca never once, in all of his writings (124 letters, plus a bunch of other stuff) never, even once, mention the existence of Jesus:

If this is heading towards Mythical Jesus, I'm out.
I'd rather spend the time picking fluff from between my toes again than waste time on that silly nonsense.
Where to begin? Probably that Xianity was a minor Jewish sect and as such barely registered on his radar. Possibly he did and the work never survived. Probably because most of the time Jesus doesn't feature in the plays he's writing any more than on my shopping lists. I mean, he got close enough to Paul's thinking to be called 'Our Seneca' so perhaps he did know something about Jesus but chose not to go with references that could be too obscure to his audience.

Why did Josephus, in his The Jewish War never once mention Jesus' existence, but yet, discuss, at length, Pontius Pilate??

Saving it for Antiquities? Despite the controversy over the references, it seems very possible that some sort(s) of comment(s) got made in Antiquities, by which time the Church was actually getting noticed.
Furthermore, Josephus had made up his mind that God had gone over to the Romans, hence the claims of Jesus to be enacting the Kingdom of God must have been false. Nothing to see here.

By the way, was Jesus crucified on Friday (as recorded in the Synoptics) or on Passover (a Thursday), as recorded in John's Gospel?

My, we're really flying around with our topics!
N.T.Wright gives a detailed argument (JVG p555) supporting John, and I think it probably works with the synoptics skipping over timing details to emphasise it as a Passover meal theologically.

Do you understand why, as a former believer, now atheist, that I do not take the existence of Jesus as being some first-century miracle worker who traveled about Palestine raising people from the dead and giving sight to the blind as a serious historical possibility??  Instead, is it not far more probable that Jesus was just some early first century apocalyptic loon whom the Romans crucified at the behest of the Jewish authorities who were in Jerusalem after Jesus started an altercation in the Temple on the Day of Passover?

Both really. Jesus was undoubtedly seen as rather unhinged for what He was claiming- to be the one through whom the Kingdom of God is enacted, especially given the way He was steering people away from the conventional military victory. The Temple action probably sealed His fate as He was getting too big to ignore.

However there is little doubt historically that those closest to Him believed that he did things they considered miracles. And there's still the not small matter of why this small Jewish sect got started with the belief set that it did. Why would they think the almighty Kingdom of God had begun, when the counterarguments- their wannabe Messiah dead on a cross, Romans still in situ, etc, are so utterly compelling?