I don't know why people so often insist that they know a certain subject when they clearly don't. For example, I don't know why people go around saying things like "we possess the works of more than 50 historians who were in Jerusalem during Jesus' lifetime," or "there are 126 ancient authors who should've mentioned Jesus if he existed, but, mysteriously, they don't," and furthermore, I don't know why so many other people take them seriously. But people do go around saying such things, and other people take them seriously, and that gives me something to do. (Not to mention making it unsurprising that someone like Bart Ehrman would compare them to tinfoil-hat-wearing people talking about UFO's.)
Clearly, some people greatly overestimate the extent of the ancient Greek and Latin literature which has come down to us. I certainly did. When I decided to read some Greek tragedies, because so many people seemed to be saying that they were a major building-block of Western Civilization, I was amazed to discover that only 33 of them have survived down to our time: 7 by Aeschylus, 7 by Sophocles and 19 by Euripides.
All together, those 33 plays form a reading assignment about the same length as the Bible. And just as in the case of the Bible, if you read the Greek tragedies you'll understand a lot more of the jokes which authors have made in the past 2400 years.
There were many more tragedies written, many more than 33. Aeschylus, Sophocles and Euripides each wrote many more than 33, and there were many other authors of tragedies working in Athens contemporary with them. However, it was not until the 380's BC, by which time Aeschylus, Sophocles and Euripides had all been dead for a while, that the Athenians began to get into the habit of performing any one of these tragedies more than once, even though for quite some time just one play could be enough to make its author rich and famous for life. This is one example of how differently ancient Greeks thought about permanence than we do. It makes us wince quite painfully to think of all of those lost plays. Back when they were written, their authors, performers and audiences had much more of a "That was great! Now what's next?" attitude.
Back to the historians: amazingly, someone said: "We possess the works of more than 50 historians who were in Jerusalem during Jesus' lifetime." and even more amazingly, some otherwise-sensible people believed him or her.
That figure is off by more than 50. Unless Paul of Tarsus was in Jerusalem during Jesus' lifetime -- and I don't see why he couldn't have been -- we possess the works of exactly zero writers of any kind, historians, theologians, lyric poets, epic poets, physicians, architects, military strategians or what have you, who were in Jerusalem during Jesus' lifetime. If Jesus existed and Paul was in Jerusalem during his lifetime, then we possess the work of 1 such writer.
If we define "ancient" as the time between the earliest writing in Latin or Greek until AD 400, when the Christians were starting to take over and things were beginning to get Medieval, then I don't know whether we possess the works of 50 ancient Greek and Latin historians, period. Unless I'm missing someone, I believe there are surviving historical works by 7 major ancient historians writing in Latin: Caesar, Sallust, Livy, Tacitus, Suetonius, the author of the Augustan Histories and Ammianus. Some would object to my calling the author of the Augustan Histories a major historian. Some would object to calling him an historian at all and point out that he seems to be posing as 6 authors and so forth, and say that he was actually writing a satire of historical writing, which unfortunately has often been mistaken for history, leading to widespread confusion and annoying generations of actual historians going back to Gibbon and earlier. I say let him be considered major until proven minor or a satirist, stipulating that for our purposes "major" does not always equal "skilled" or "accurate."
We have the works of some other ancient Latin historians, but these are mostly people who condensed parts of Livy's work: Florus, the anonymous author of the periochae, Julius Obsequens, etc. We currently possess about 1/4 of Livy's work; if we find the rest, the interest in Florus and the periochae and Julius Obsequens will presumably drop drastically. In earlier eras Livy was considered to be Rome's greatest historian. Nowadays the overwhelming favorite is Tacitus. Writers' reputations rise and fall and rise again. Others made similar Reader's Digest Condensed Versions of Tacitus and other major historians. They are called minor historians. Curtius Rufus translated some Greek material -- now mostly gone -- on the life of Alexander the Great. Some of the work of Cato the Elder survives, but not his history of Rome which was so much admired by other Roman writers. Counting major and minor writers, in Latin and Greek, I don't know of 50 ancient historians. I'd have to branch out into other languages and/or the Middle Ages to reach a total of 50.
Of course, historians glean all sorts of information from other types of writing than the historiographical. Considering the contributions of Cicero, Pliny the Younger, Symmachus, various Emperors and others, the other genre of most use to historians may be letter-writing. I grimaced as I wrote that because I can't stand Cicero. I consider it to be a crying shame that barely 100 pages of Sallust's writing has survived, while we have thousands of pages' worth of that thoroughly ordinary guy, Cicero. I'm sure several readers grimaced as they read the preceding 2 sentences, but I'm not going to sit here and lie to you about my opinion of Cicero. Today Cicero is probably still considered by most to be one of the very finest writers of Latin. In the Renaissance Cicero was beyond a doubt far and away the single most highly-admired Latin author. For many people writing in Latin in the Renaissance, good Latin writing equaled imitating Cicero. Like I mentioned above, writers' reputations rise and fall. Cicero's reputation as a genius of a author has fallen noticeably since the Renaissance, and I consider that to be progress and hope it continues, so there.
If anyone thinks I'm completely wrong and that people are right who are claiming that we have the works of 50 historians who were in Jerusalem between ca 6 BC and ca AD 40, or that there really are 126 or more ancient authors from whom the absence of any mention of Jesus is downright suspicious, they are of course more than welcome to comment. I could use a good laugh.