What delighted the Greeks with the victory over the Persian kings Darius and Xerxes?

They rejoiced at the victory over the Persian kings, because it meant that their homeland was saved. They were able to repel the invasion of an external enemy. The following important events should be noted here:

Battle of Marathon, it took place in 490 BC. Then the Greeks first defeated the Persians under the command of Darius 1;
Battle of Salamis, here the Greeks defeated the Persian fleet;
Battle of Plataea, it took place in 479 BC and was a general battle of the Greeks with the forces of Xerxes.