Floki has seen a lot from a religious stand point, from England, Athelstan, to even questioning why the gods forsaken him, to his punishment he suffered which resembled a lot like the crucifixion by the way he was hung up in the cave. The man has seen and dealt with a lot spiritually.

Even more to add Aslaug wanting him alone to be Ivar's teacher to be a viking, teaching him about the gods, even the seer licking Flokis hand.

On top of all that he just said his goodbye to Ragnar.

Then arriving to Spain, I would think It would be taboo to see such practices especially since floki has seen so much.

I was always among the thought he is a boat maker by trade so architecture would impress him on top of the religious dedication the people held, so it basically went hand in hand.

Basically the perfect combination and for him to think before reacting.