The lapses and manipulations by the authorities may well be due to the Mandalay Bay, local government and law enforcement, and the Feds all wanting to shape the facts so that they can avoid getting sued or held at fault as a matter of public opinion. The lack of substantial leaks from the investigation suggests that no more than routine CYA is involved.
The city of Las Vegas is covering for the Mandalay Bay casino. They allowed Paddock to bring over 20 guns up to his room because he was a high roller, and he had the do not disturb sign up for a few days.