STUPID: They wanted to track them, but were incompetent.
EVIL: They did not intend to track them in order to use the resulting bodybags to bolster the argument for taking away RKBA in the USA.
CORRUPT: They were allowing the guns to go to the Sinaloa cartel, and were taking sides in the war between CDS and Los Zetas.
Because of all the alphabet agencies involved, I'd say all three. Each individual involved had his/her own agenda. One of them is making money helping the drug cartels.
The audio tapes already show they did not intend to track them