You say -- One cannot even make a case that Jesus was a non-entity, and some individual or small group just made up the story about him.
Nonsense. Many have done so.
You say -- In order to make that fly, one must explain why said individual or group would make up such an elaborate and blasphemous story, and then meet the even greater challenge of explaining how he/they could have been so successful in such a short time as to convince everyone, friend and foe alike, of the historicity of the basic facts, in spite of the fact that there were many people still alive who were in Galilee and Jerusalem at the very times Jesus was supposedly doing all those incredible and news-worthy things. We do, after all, live in a world in which human beings live for a number of decades, and are endowed with this faculty called "memory".
For that argument to have much weight or merit, It must have been likely that some residents of Jerusalem or Galilee in around the year 30 may have both witnessed the events in the gospels as well as actually being exposed to those gospels.
For that to have happened, first one would have to have been in Jerusalem or Galilee and witnessed some of the alleged events of Jesus. Though the gospels give the impression that those events were "news-worthy" of the time, the actual historical records don't support that. There is scant mention of Jesus in one controversial paragraph of Josephus, and no mention of any church that grew up around his teachings. Yet, a number of historians have described many Jewish sects of the time. The monastic, reclusive Essenes were described at length by Josephus, Philo of Alexandria and Pliny the Elder. Philo called the Essenes, "athletes of virtue" and Josephus referred to them as "saintly". Yet, no mention is made of the followers of Jesus and the 12 apostles. One must assume that they "flew under the radar." So, unless someone was actually present and at the same time where and when Jesus supposdly was present, that resident would have little reason to doubt the story, since he was not there.
Thus, a Jerusalem or Judaean resident, to dispute the gospels, would have had to likely personally been able to witness one of the events of the gospel, such as being at the temple at the time before Passover during Jesus's alleged scene with the money changers, or along the road or at golgatha when he was crucified, and even then, would have had to inquire the name of that person.
He would also then have had to been exposed to the gospel story about Jesus. Now, if there were in fact no Jesus, then the earliest known stories of what Jesus allegedly did in Galilee and Jerusalem didn't appear until Mark's gospel, which was written most likly in Rome. From Paul's letters and the other NT epistles, there is no hint that they claimed or believed Jesus had just walked the earth, that he did anything related in the gospels, or that he was crucified under Pilate.
Thus, for this argument to fly, a person would have had to both personally been at the temple, or at golgatha, or somewhere else Jesus allegedly was, then would have to been exposed to Mark's gospel. Now, tradition holds that Mark's gospel was written in Rome, sometime after Peter's death, putting it around 68 AD. This means that someone who was at the temple or at golgatha, and saw nothing out the ordinary happen that particular day, would have to remember that ordinary day for 40 years. He would have had to then have survived the Jewish War. In that war, Jerusalem was seiged and then sacked, and its residents either slaughtered or scattered. Estimates of the deaths in Jerusalem were between 2/3 and 1-1/2 million. Outside of Jerusalem, there was extreme carnage as well. The Jewish residents of 9 of the 10 cities of the Decapolis were slaughtered -- only in Gesera were they allowed to flee. Josephus relates an account of a major battle between soldiers of the Roman X legion and rebels in Capernaum, Peter's hometown, in which the number of Jews killed was estimated at 6,300. There were a number of battles in Samaria, again with large losses of life among the Jews.
So, the few who may have been in some certain spots around the year 30, would have to remember for 40 years that it was an ordinary day, and then survive the Jewish War. If they were of the lucky ones who did, they then would somehow made their way to Rome (when they were at least in their late 50's). There, they would have to somehow become involved in or exposed to a little-known Jewish sect called christians, and been exposed to their gospel.
Even then, they would have had to write to somebody about it. This in itself is problematic, since most people of the time were illiterate, and papyrus was relatively expensive. And who would he write to? Even if that person did remember what little happened that passover 40 or so years earlier, the folks back in Judaea had much bigger problems to worry about than some claims about some obscure messiah character worshipped from 40 years earlier in some sect in Rome. But even if he did write about it, that letter then would have survived 2000 years, or at least made its way to some rabbi in the diaspora to comment upon, and then that rabbi's account to have survived until today.
Thus, if Jesus didn't exist, there is little surprise that no letter or account of a Jewish resident of Judaea disputed the gospels. Someone would have had to been at one of the biblical scenes, and then remember for 40 years that nothing out of the ordinary happened that day, then survived the carnage of the Jewish War, then found their way to Rome, been exposed to an obscure sect, been exposed to their gospel, have written to someone about it, and that letter to have survived, directly or indirectly, up to today.
