Weapons of Mass Destruction

I see Berkshire Hathway's earnings were affected by the giant derivative that Warren Buffet bought for the company a few years back.  His explanations in the annual reports of BKHT are not convincing that this instrument is other than a useless financial exercise and certainly not an example of masterful capital allocation.  I don't see the material good it provides society nor the company.  It's not remotely like buying Union Pacific, for example, which appears to be a terrific investment nor USAIR which was a terrible one but which at least was an investment and not a wager.