What kinds of business conduct prompted business ethics to become a field in its own right?

Recurring scandals where perfectly legal-looking commercial logic produced plainly indefensible outcomes — insider trading, dumping harmful products on weaker markets, resource extraction, and restructurings that wrecked staff for avoidable reasons.

Business ethics did not grow out of philosophy seminars but out of events that demanded a response. Four recurring patterns:

• Insider trading — large profits taken on the stock market by exploiting information the counterparty doesn't have. The transaction is voluntary on both sides, which is exactly what makes it a good test case for "is consent enough?"
• Double standards across markets — marketing pharmaceutical products in developing countries although they are known to have problematic side effects there. The regulatory gap is real; the question is whether its existence licenses using it.
• Resource extraction — forcing the pace of extraction by exploiting raw-material sources in poorer countries without restraint, with the costs landing on people who don't see the revenue.
• Restructuring — strategic reorganisation carried out in a way that inflicts severe and avoidable burdens on employees. Note the word: nobody disputes that restructuring is sometimes necessary; the ethical question is the "avoidable" part.

The common thread is that in each case the conduct was rational by the firm's own metric and harmful by almost any other. That gap is the subject matter of the field.

Go deeper:

• Transparency International: What is corruption? — the working definitions and the mechanisms behind the cases that built this field.
• Wikipedia: Insider trading — the cleanest test case: both parties consent, and it is still widely held to be wrong.
• NZZ: Korruption im Seco — Mitarbeiter zu 4 Jahren Haft verurteilt — a Swiss federal procurement-corruption case, start to sentence (German).