^18:2 With a mighty voice he shouted:

“‘Fallen! Fallen is Babylon the Great!’^[a]
She has become a home for demons
and a haunt for every evil spirit,
a haunt for every unclean and detestable animal.

With a mighty voice he shouted:

This is not prideful bluster but a mighty voice of a 'presence' angel speaking with GREAT AUTHORITY (previous verse).

“‘Fallen! Fallen is Babylon the Great!’^[a]

This angel proclaims the collapse of the socioeconomic order even as the 7 puppet leaders have just subdued any "organized" religion (Revelation 17:16). Only worship of the antiChrist/devil is permitted at this time.

E. W. Bullinger in "Commentary on Revelation" explains that the "FALLEN" may take longer than seven years. That is, the complete destruction of the socioeconomic order may precede or succeed the 7 years Tribulation period. Even in the Old Testament the time span for the demise of Babylon is indeterminate (Jeremiah 51:1-8-10).

She has become a home for DEMONS

These 3 points confirm this "FALLEN" is primarily a collapse within the evil spirit world. Ever since the seven bowl plagues came out of the temple in heaven (Revelation 15:6), the emphasis in Revelation is on the dissolution of evil on this earth. Implied in this is that the socioeconomic system is riddled with demon possessed persons.

Contrast this with the believer's dwelling (Ephesians 2:19-22).

and a haunt for every EVIL spirit,

The politicians and businessmen cannot free themselves either from the mark of the beast, which they need to do business (Revelation 13:17) or these EVIL SPIRITS.

a haunt for every UNCLEAN and DETESTABLE ANIMAL.

According to Revelation 19:17-18, the very being of these political, military, and business leaders will be consumed by these ANIMALS/BIRDS (the evil one). Jesus, himself, referred to these ANIMALS/BIRDS as the 'evil one' (Matthew 13:1-9,18-23). Isaiah 13:17-21-22 names these birds as owls and ostriches (silent flyers and cantankerous nonflyers). These socioeconomic leaders are in prison with these ANIMALS/BIRDS. It's an imprisonment of evil with a touch of deceit (Jeremiah 5:20-27-29).

^[a] Isaiah 21:9