The Jesus Myth Theory did not just appear with the popularization of the internet, although that has been influential in its spread. An important figure in the development of this theory was Bruno Bauer (1809-1882).
Bauer was an influential figure in the 19th century, crossing paths was some of the most important people of that era. Between 1839 and 1841, Bauer was very close with Karl Marx, although there was a serious break in their relationship. Later on, a young Friedrich Nietzsche came to Bauer seeking advice/
It should be noted that Bauer was a Hegelian philosopher and not a biblical scholar. It is true that in the 19th century that things were not as specialized as they are today, but it is also true that Bauer’s views of Jesus came through a Hegelian lens.
Bauer was working in an environment that had become increasingly skeptical of the Bible. Many German scholars were looking at the Gospels and attempting to reconstruct what the real Jesus looked like.
Bauer began with the Gospel of Mark, which he dated 117-138. Despite this late date, Bauer saw Mark as the earliest Gospel, a view that is held by many scholars today. Bauer held that the author of Mark was the one person responsible for coming up with the fiction that we know as the story of Jesus.
Bauer saw Mark as a blending of Jewish ideas and pagan writings. To make things even more extreme, Bauer rejected all of Paul’s letters as later forgeries.
It should be noted that there is no evidence that Bauer was an orthodox Christian. It is also interesting that Bauer wrote on the French revolution, the time when the existence of Jesus was first doubted.
Many modern mythicists owe a debt to Bruno Bauer, even if they are not aware of his role in developing the Jesus Myth Theory.
If you are interested in learning more about Bauer and his era of Jesus studies, I recommend Albert Schweitzer’s Quest of the Historical Jesus.
Bruno Bauer was certainly a Bible scholar. He taught biblical scholarship, his primary publications were biblical scholarship, and his training was in theology. He was theology and Bible scholarship faculty basically up until his license to teach theology was revoked following his books causing too much strife.
Now yes, he viewed the Bible through a Hegelian lens, but this was essentially his critical theory basis on how to methodologically evaluate things (Hegelianism later had effects on most historians in Germany, the UK, France, etc. and resonates in historical studies today, I might add, with theories of dialectics especially being prominent).
Also, there is evidence of Jesus being doubted as early as the 1620’s. Here is a booklet written on the subject of mythicism before Volney, and it is really cheap (and written by a historicist as well).
https://www.amazon.com/Earliest-Mythicist-References-Christopher-Hansen/dp/B08F6Y54B4/ref=tmm_pap_swatch_0?_encoding=UTF8&qid=1625330731&sr=1-1
If I am not mistaken, Bauer was also an early member of the Bavarian Illuminati.