Larry Hurtado is wondering why the Deists’ theological assumption about what constitutes a valid starting point for Christology should continue to carry the day, even among traditional believers?
Now the interesting bit is that this (originally Deist) argument was wildly successful, at least in setting the terms of the ensuing theological and scholarly debate. That is, even those (e.g., advocates of traditional Christian faith) who opposed the Deists’ conclusions accepted their terms for the debate that followed (right down to our day): Jesus’ own teaching about himself was the criterion of legitimacy for any claims about him.
So, what you have is a fundamentally theological issue becoming the shared assumption for a great deal of subsequent historical investigation. And the result, as I’ve said, was a great deal of mischief: Christian apologists producing contorted historical arguments trying to pump up maximally what might be attributed to Jesus, and critics of traditional Christian faith…contending that these claims were invalidated by the evident historical events/process through which they had emerged.