Because you only get his side of the story, you don't know if the reason he was fired was because the other devs knew it wouldn't take that long to fix, or because he had some negative history with the company.
I'm not writing the guy off here. It just pays to be wary with stories like this that end with "and then i was fired", because the outcome and tone of the story automatically makes the reader feel that there is some sort of residual bitterness that has shaped the author's view negatively.
But I suppose if you get fired you have every right to be bitter about it too.
I doubt they would fire a QA tester just for finding a bug. He might have been laid off with a bunch of other people or he might have been getting a big head about his prize defect. Granted, it is kind of a big defect. But some people can be sore winners.