Why did Elihu burn with anger against Job, according to Job 32:2?

Answer: He justified himself rather than God

Elihu was angry with Job "for justifying himself rather than God," and with the three friends for failing to refute Job (Job 32:2-3).

“This kindled the anger of Elihu son of Barachel the Buzite, of the family of Ram. He burned with anger against Job for justifying himself rather than God, and he burned with anger against Job’s three friends because they had failed to refute Job, and yet had condemned him.”— Job 32:2-3 (BSB)