The two officials were executed in a gruesome way; the verse literally states that they were hanged on the wood.
This might refer to hanging, crucifixion (a Persian invention), or impalement.
Quite disappointingly, Mordecai was not remembered or rewarded for his deed of loyalty. But God, who holds times and occasions in his hand, ensured that Mordecai’s name and deeds were recorded in the annals of the king. These annals would later play a crucial role in Mordecai’s fate and that of his people.
23 When the affair was investigated and found to be so, the men were both hanged on the gallows. And it was recorded in the book of the chronicles in the presence of the king.