Reading again Bruno Bauer, it seems that he considered the baptism of Jesus by John as a late addition in Mark:
In order to shape the development of the work of salvation historically, the rounding off of the historical view required that the beginning of salvation also be proven, i.e. the point in time when the Lord replaced the Baptist and began his task.
By definition, the "the rounding off of the historical view" requires that the original story was still not "rounded off" enough. I.e. it was without the baptism of Jesus by John.
You must be mistaken. Read the text again (italics are mine):
Apart from the report of Mark, in which the original view has been preserved, which is the basis of the later reflection work of Matthew and the Fourth Gospel, there is not a single testimony for the "Factum" of this baptism
Following this remark, Bruno Bauer is arguing that only after the congregation started to have faith in Jesus' sacrificial death and resurrection and wanted to put it in a historical context, they found a need to fix the point in time where the Jesus began his salvific task. Hence the emphasis in John on Jesus' baptism as the moment of divine favour.
Baley wrote: ↑Sat May 20, 2023 8:51 am
You must be mistaken. Read the text again (italics are mine):
Apart from the report of Mark, in which the original view has been preserved, which is the basis of the later reflection work of Matthew and the Fourth Gospel, there is not a single testimony for the "Factum" of this baptism
Following this remark, Bruno Bauer is arguing that only after the congregation started to have faith in Jesus' sacrificial death and resurrection and wanted to put it in a historical context, they found a need to fix the point in time where the Jesus began his salvific task. Hence the emphasis in John on Jesus' baptism as the moment of divine favour.
I see a problem in that 'after', since I assume that the congregation, according to Bruno Bauer, "had fait in Jesus' sacrificial death and resurrection" even before the need of "putting it in a historical context", accordingly it is possible to interpret Bauer as saying that in proto-Mark there was not still at all the need of a "historical"/chronological context, but merely a story without chronological markers at all.
Further evidence that I am right in my reading of Bauer, is that Bauer himself claims that Paul didn't know the baptism of Jesus by John.
Now, according to Bauer, Paul never existed, and the false "Paul" writing in his name is therefore the guy who is ignorant of the baptism of Jesus by John.
This false "Paul", according to Bauer, knew already the Earliest Gospel (=proto-Mark, for Bauer).
Therefore the conclusion is sure, that Bauer is claiming that the baptism of Jesus by John was a late addition, made on proto-Mark, from which the result was our current Mark.
Though your reconstruction is not evident from the chapter quoted, that might well be the case; we don't know proto-Mark. Nevertheless as Bruno Bauer quite brilliantly illustrates, the baptism story is another jarring gospel element that had to be smoothed out over time.
