The recent release of the long-awaited government report on the May 6 “flash crash” highlighted one specific trade as the catalyst for a series of chain reactions, accelerated by computer algorithms, that whipsawed the market. While the report goes a long way toward explaining the events of that afternoon, it doesn’t begin to address the systemic weaknesses of the market, highlighted by the nearly 600-point drop in the Dow Jones industrial average in a matter of minutes — and the Dow’s even faster recovery.