No, he is also mentioned in other texts from the same period (see below).
It is certainly not bad scholarship, you simply need to know how antique text corpora works (and the bible is, religious or not, an antique collection of texts) and under what circumstances the text in question was produced. Religious texts are as useful for historical studies as the "real" ancient annals and histories are. I would guess that The Bible and Herodotes histories contain about the same amount of facts. Not to mention the early history of Rome in Livy. Anyway, on Jesus and Christianity; there are actually many and surprisingly early references to the Christians - only a couple of decades after his death - in the Roman literature (too many to be listed here) although references to Jesus himself are rare. He is, however, mentioned in Josephus history of the Jews:
"Festus was now dead, and Albinus was but upon the road; so he assembled the sanhedrim of judges, and brought before them the brother of Jesus, who was called Christ, whose name was James, and some others, [or, some of his companions]"
Josephus - Antiquities of the Jews XX. 9.
This event is said to have taken place under the rule of Herod Agrippa I, i.e. 37-44 AD, not long after Jesus death. And on the brother thing, take a look at the dead sea scrolls for more information on Jesus brothers (e.g Thomas).
It is, in the end, quite inconceivable that a small cult would spring out of nowhere in the 30's-50's AD by inventing a characters life, describe it in several gospels and tie them to historical events and characters. Then add that the main character, i.e. Jesus, would also be mentioned in other texts - and we know for a fact that there were several Messiahs in Judea during the period, so the though of one of them actually becoming famous is not far fetched.
It would have been, had Christianity been a cult invented by the ruler, possible that Jesus was fictional, but it wasn't. Christianity came from "middle-class" Jews with no major influence and no aim but to spread the faith, there are no indications of the Apostels getting rich so to speak (getting killed under horrible circumstances seems to have been likelier). And they were not trying to create a uniting religion for the empire (as some later emperors), they had no such interests.