How Could the Similarities Between Krishna and Jesus Be a Coincidence?

Questions about how the similarities between Krishna and Jesus could be a coincidence and whether there’s any proof to substantiate the idea that Jesus studied Buddhism during his “missing years.”  

• How could the similarities between the Krishna story and the Jesus story (e.g., a star at his birth, his father traveling to pay taxes, a transfiguration, etc.) be a coincidence?
• Is there any proof to substantiate the idea that Jesus studied Buddhism during his “missing years”?