They didn't. All they did was fail to follow up on known straw purchases. Nothing was "sent". Nothing was "actively" done. The ATF and DOJ weren't loading crates of AKs and ARs into trucks and driving them in to Mexico.
Not defending it at all...but let's not overstate what happened. Known straw purchases were made that the ATF knew were intended for the cartels. ATF let the purchases happen, and never did anything about it.
The ATF DIRECTED FFL's to complete the sales. That is a positive action, not passive. Plus, you completely ignored all the other evidence that doesn't support you head in the sand theory.