What feels more off to me is why does the king have a cross? And why does a religion use the murder weapon of its messiah as its main logo? What if He was killed by a rock or a rifle or a guillotine? What would the king be carrying on his head?
1. Because many ancient monarchs claimed they had divine backing as the basis of their right to rule. A ruler wearing religious symbols strengthens that association. Chess kings from non-christian countries don't have crosses but go with other symbolism.
2. Because the most famous miracle performed by Jesus is that the crucification didn't stick: he rose from the dead after a few days and ascended to heaven not much later. So the cross is not so much a murder weapon as a callback to the central promise of christianity: that believing will grant you eternal life in Heaven after you die. It should be noted that early christians didn't really use the cross as a symbol btw, that came much later.
Something is __very__ off here ...