John Gill Commentary Esther 3:6

"But he thought scorn to lay hands on Mordecai alone; for they had made known to him the people of Mordecai: wherefore Haman sought to destroy all the Jews that were throughout the whole kingdom of Ahasuerus, even the people of Mordecai." — Esther 3:6 (ASV)

And he thought scorn to lay hands on Mordecai alone
That would not be a sufficient gratification of his revenge; he was too low and mean a person only to wreak his vengeance on; nothing short of his whole nation would satisfy him:

for they had showed him the people of Mordecai ;
that they were the Jews; for Mordecai had told the king's servants, that talked with him on the subject, that he was a Jew, and gave that as a reason why he could not and would not reverence Haman:

wherefore Haman sought to destroy all the Jews that were throughout the
whole kingdom of Ahasuerus ;
even the people of Mordecai; and that not merely to be revenged on Mordecai, but because he plainly saw, that both by his example, and upon the same principle with him; they would all to a man refuse to give him reverence; and therefore he was resolved to root them out of the whole empire, that he might not be mortified by them.