Whether Jesus existed or not as an actual person really is a matter of nothing more than historical interest.  Even if such a figure existed as a kernel around which myths evolved, the mythical Jesus never existed, and that is the one of interest.

The same thing can be said about Mohammed, who almost certainly existed as a real person but who did not do many of the things recounted about him, or of the Buddha (about whom there is less certainty).

This is a common thinking error in historiography -- that the existence of a myth tells us anything about history.  It doesn't.  Sometimes there is a historical kernel, but usually there is not, and we have no way to know.  There was no Troy, no Achilles, no Hercules, no Robin Hood, no King Arthur.  Since one cannot prove a negative, one cannot prove this, but one should assume it until there is good evidence otherwise, and the existence of the myth is not good evidence, especially if it contains miraculous or similar stuff.