In the Bible, it says that love of money is the root of all evil. That certainly seems to be the case in Arthur Miller's All My Sons. Virtually everything bad that happens in the play comes about as the direct result of the unthinking pursuit of riches.
Take the example of Joe Keller. A basically good man, his soul has been corrupted by the love of money. He's realized that he can make a lot more money by shipping what he knows full well to be faulty plane parts to the military.
Deep down, Joe must know that there's a real chance that people will die as a result of his actions. But he's so overcome by greed that he's not really thinking about other people's welfare. So he goes right ahead and keeps on supplying the Air Force with cracked cylinder heads, with fatal consequences.
In order for Joe to be corrupted by money, he must first of all be an essentially decent man. And all the available evidence points in that direction. He comes across as a decent, loving family man who just wants what's best for his children. Unfortunately, he becomes so overwhelmed by an insatiable desire for money that he ends up putting the lives of pilots at risk, including that of his own son Larry.