Charles Ellicott Commentary Jonah 1:10

"Then were the men exceedingly afraid, and said unto him, What is this that thou hast done? For the men knew that he was fleeing from the presence of Jehovah, because he had told them." — Jonah 1:10 (ASV)

Why hast.—Rather, What is this that you have done? The question expresses horror, not curiosity.

For the men knew that.—Jonah’s answer in Jonah 1:9 is evidently intended only as an abbreviation of what he actually replied.