1)
Why did he get angry only after he saw that Mordechai does not bow? Did he not believe them?
1.
Vilna Gaon: Initially he thought that perhaps Mordechai does not bow because he thinks that Haman does not notice. He came close, to show that he oversees this, and even so, Mordechai did not bow.
2.
Malbim: Now that he was close, and still Mordechai did not bow, he knew that it is due to hatred - "Ein? Mishtachaveh Lo." Haman's honor irks Mordechai.
