They should have gone after the Phoenix Division first, gotten a few folks to roll, then gone up the chain. Instead, they wanted to implicate the entire executive branch, and they failed.
It soon became evident that Fast and Furious was the brainchild of the Phoenix division of the BATFE and an anti-gun federal prosecutor. The Phoenix BATFE was an out of control government office managed by rogues who sold Fast and Furious to their agency bosses: Grassley and Issa never got behind this fact. In their zeal to implicate Holder and the administration, they turned their investigation into a hunt for who knew what when. They failed miserably.
IMO: The greatest mistake of Grassley and Issa was their failure to demand a reorganization of the BATFE.
After the contempt citation Fast and Furious became a dead duck, as i predicted.