The same thing as “Who let bro cook?” except it’s blaming the Fallen Angels for it. A reference to the Dead Sea Scrolls.
It’s used when someone sees something that can be considered an amalgamation, abomination, or something that shouldn’t really exist hypothetically or literally.
Person: “What the f*ck is that?!”
*Sees something that probably shouldn’t exist.*
Person: “Who let the Fallen Angels cook?!”