"Why did the FBI led by Jim Comey allow a known terrorist to buy assault rifles?"
Maybe.....
- They are spread so thin investigating the 1,000 cases involving ISIS in the US, and the problem of hundreds of UN-vetted Syrian 'refugees' coming in every day that they missed this one.
- Having to deal with Hillary's illegal activities on top of all their other duties is too distracting / much of a burden.
- They are being handcuffed by a President, AG, and DHS who believe - despite an Islamic Extremist just perpetrating the US's largest terrorist mass shooting in the US - that AMERICANS (Conservatives) are the biggest threat (that and Global Warming) we have to look out for.
** To work for the DHS, Mateen had to go through an extensive background check...proving once again Obama HAS NO 'vetting process' capable of finding terrorists / extremists and/or protecting Americans.
** Adding fuel to the fire of which the FBI / DHS finds itself standing in the middle is WHY did this administration not detain Mateen's wife? After interviewing her, they failed to keep tabs on her, and now she has disappeared....and now they know Mateen and his wife were texting each other while he was slaughtering people in the club.