One of the more interesting parallels between Christianity and Buddhism to me is how both religions’ emergence coincides with the development of paper record-keeping. Get much closer to today, and the lack of historical records surrounding the holy figures more and more points to chicanery on the part of early believers. Much further back and it starts looking like Hinduism or Judaism, with any sort of historicity impossible simply because there’s no way for anybody to gather any historical evidence whatsoever as to the actual events.
So while there really isn’t the kind of historical evidence we would like to have concerning the Buddha, such evidence would have only been created for matters of importance to the state, early religion would have been inconsequential to them just as early Christianity was to the Romans, there’s plenty of history available to point to the general time period so we can paint a broader picture of what a hypothetical Buddha would have been all about, then try to reconcile that with the actual picture the Buddhist scriptures painted.
But detailed questions concerning the founders of cusp-of-history religions will never have satisfactory answers. No written records concerning the Buddha exist until some 300 years after his death. The only thing we can have is answers derived from the scriptural and religious sources.