One reason is that they were open to new ideas. The reason why they were open to new ideas is because they could get new or good ideas for the war and the could have a better chances to win the war with new ideas.
Another, reason is because their city was on water. The good thing of having their city on water is people from all around the world could come on a boat and give them ideas. But on the other hand Sparta liked to live on the mountains were it was harder for people to go because they thought that if they get new ideas that