They worshiped the dragon because he gave authority to the beast.

And they worshiped the beast, saying,

"Who is like the beast?

Who is able to wage war against him?" 

Revelation 13:4

And I looked, and there was a pale green horse.

The horseman on it was named Death,

and Hades was following after him.

Authority was given to them over a fourth of the earth,

to kill by the sword, by famine, by plague,

and by the wild animals of the earth. 

Revelation 6:8

(Holman's Bible)

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