Keep this in mind, the AATIP (the Advanced Aerospace Threat Identification Program) didn’t get shut down, it just stopped receiving funding, however, it is still receiving funding from the CIA and the Navy.
So the CIA / Navy / DoD is still researching UFOs. This basically means that Luis Elizondo, the former Director of the AATIP reported to the DoD / CIA / and the Navy, the moneypushers for AATIP. Elizondo said he was kept from reporting everything he wanted to Secretary Mattis. We can conclude it is very likely it was the CIA that wanted to keep Mattis in the dark about some stuff.
Here’s a new interview with Luis Elizondo