As to why I bring this up, consider: if I asked you whether the Celts of Gaul or Britain had been in close contact with the ancient civilizations of the Middle East, what would you have said? Through Iberia, they were. These statues are only the most famous signs of contact that was frequent and endured for centuries. Other evidence of contact abounds, from Phoenician glass in Celtiberian tombs to the fact that much of Hannibal's army was made up of Celtiberian soldiers.
European historians used to believe that whatever bits of Middle Eastern civilization reached Europe did so by way of Greece, but that is not so. There were many connections in the ancient world, like the ones that somehow carried the Chinese tale of Cinderella to Europe, or Babylonian astronomy to Bronze Age Germany, or the goddess Astarte to Spain.
The ancient world was a connected world, and the same links that carried tin from Cornwall to Italy, amber from the Baltic to Egypt, and glass from Egypt to Ireland, could also have carried images and ideas. So if certain motifs in early medieval Celtic stories resemble Christian lore, that might indicate a direct borrowing from Christian sources. But then again it might be that both derive from an older stratum of Middle Eastern legend, the source of things like the Flood, Jacob's Ladder, and much about our traditional image of the Virgin Mary. The virgin birth, the rebirth of the divine son, holy water that purifies – these are ancient, ancient ideas, and they could have spread around the world in many ways. The elite of pre-Roman Gaul and Britain were not isolated bumpkins, but the leaders of an old, literate civilization with ties to many other peoples across Eurasia.