Why do Christians believe that skeptics are obligated to provide evidence for THE true, natural, alternative explanation for the empty tomb and the early Christian belief in a resurrection? We are under no such obligation. We are under no obligation to provide evidence for what actually happened, only to point out that alternative explanations are possible that explain all the evidence available. We are also not obligated to prove that our alternative, naturalistic explanations are more probable than the Christian supernatural explanation as probability is a matter of opinion.
Bottom line: If skeptics can demonstrate that there are possible alternative, non-miracle explanations for the early Christian belief in a Resurrection, then the onus is on Christians to prove that their extra-ordinary (supernatural) explanation is more probable than these naturalistic explanations. Christians may not like having the onus put on them, but that is how things work in our culture.
Let me give an analogy:
Farmer Brown’s cow is missing. Police investigators cannot find any trace of her. The only lead that exists is the claim by twelve members of a local, newly formed religious sect who state that all twelve of them watched as the milk cow levitated one hundred feet into the air until disappearing inside a Martian mothership, which once the cow was inside, sped off into the night sky at the speed of a jet airplane.
Question: Should we believe the Cow-abducted-by-Martians story simply because there is no evidence for any other explanation??? Of course not! Just because there is no evidence for any other explanation does not mean that the most PROBABLE explanation is the very extraordinary, never-heard-of-before claim of a group of religious fanatics. The most likely explanation for the missing cow is the same explanation for most missing cows: It was stolen or something ate it.
Most educated (sane) people would not insist that skeptics of the cow abduction story provide evidence of a more probable, natural explanation before assuming that a more natural explanation is the cause of the missing milk cow.
Christians need to apply the same logic to their missing Jewish preacher story.