One individual with direct experience of life in Palestine -- say, Paul -- suffices to write down a story with geographical details. As many people as you like may then crib from such a story. But we do know of more than one person who had lived in Palestine, in the period.

I do not judge theories. Historians judge, and report their results. As I understand the scenario, the theology came first, then the parables, then a person to quote parables from, and finally biographical accounts of that person's life, all unfolding over decades according to the needs of an expanding church.

I do not find anything implausible in their results, or in their reasoning. You are welcome to your own conclusions. If you have a problem with historians' results, you may take it up with them.