Why is the following phrase ironic "surveying his handiwork," as found in Harper Lee's To Kill a Mockingbird?

In Chapter 17 of Harper Lee's To Kill a Mockingbird, the narrator Scout uses verbal irony when she describes Mr. Bob Ewell as "sitting smugly in the witness chair, surveying his handiwork."

Verbal irony is created when a writer or speaker uses a word to mean the complete opposite of what the word literally means.

Prior to Scout describing Mr. Ewell as "surveying his handiwork," Scout gives a narrative description of his testimony to Mr. Gilmer, the prosecuting attorney, while on the witness stand. When Mr. Gilmer asks if Mayella was screaming, Mr. Ewell describes that he heard her screaming while he was gathering firewood, dropped his load of firewood, and raced to house's window to see what was going on. He then ends his testimony with a grand finale using words that are not appropriate for a formal courthouse setting, as Scout describes in the following:

He stood up and pointed his finger at Tom Robinson. "--I seen that black nigger yonder ruttin' on my Mayella!" (Ch. 17)

Mr. Ewell is proud of himself because, being low class and uneducated, he thinks he has convinced his audience of his claim by using his foul language; hence, in her narration, Scout uses the word "handiwork," which literally means "the result of work done by hand," to depict Mr. Ewell being proud of his accomplishment (Random House Dictionary).

However, Judge Taylor thinks differently about what Mr. Ewell has accomplished through his obscene testimony and so does Scout, along with the rest of the courtroom. Hence, Scout, in her narration, ironically uses the word "handiwork" to mean the exact opposite, to show that Mr. Ewell had really accomplished nothing except to create bedlam in the courtroom. Furthermore, after Mr. Ewell's statement, Judge Taylor raps on the bench with his gavel for a full "five minutes" to quiet the courtroom and eventually gives Mr. Ewell the edict to "keep [his] testimony within the confines of Christian English usage, if that is possible" (Ch. 17).

Hence, the phrase "surveying his handiwork" is ironic because Mr. Ewell is actually doing the exact opposite; he is surveying the bedlam he has created.