OMAHA, NEB. — Warren Buffett is a called an oracle and a cult hero not just because he’s made himself one of the world’s richest people, but because he comes across as folksy and, above all, honest. Now, he’s found himself in the unusual position of having to explain a top Berkshire Hathaway executive’s questionable behavior.

The situation: A key executive thought to be a potential successor to the 80-year-old Buffett persuaded Buffett to buy a chemicals company that the executive had personally invested in. The executive, David Sokol, saw his investment grow by $3 million, or 29 percent, after Berkshire bought the company, Lubrizol.