13:4and they worshiped the dragon, because he gave his authority to the beast; and they worshiped the beast, saying, "Who is like the beast, and who is able to wage war with him?"

This is a continuation of the previous verse.

and they worshiped the DRAGON,

The devil thinks he finally has succeeded! The people are worshiping him. But verse 15 indicates not all do. However, most people who are left do (believers are gone if you believe in pre or mid tribulation rapture (Revelation 4:1); the two witnesses are gone (Revelation 11:12); and the 144,000 witnesses apparently are gone too (Revelation 14:3)). So there are very few whose names are written in the book of LIFE who are left. For what purpose, we can only ponder.

because he gave his authority to the (sea) BEAST;

How or why people gravitate to authority and power is an interesting psychological study of its own.

and they worshiped the (sea) beast, saying,

This is the sea beast who got his power, throne, and great authority from the devil (verse 2).

"Who is like the (sea) BEAST, and who is able to wage WAR with him?"

Why is it that the world thinks that conquering by force means victory? Could it be that when the devil only has the earth as his domain, then he will "defend" it by force? Apparently, he has discovered (or bought) the ultimate weapon (probably the atomic bomb or some other doomsday weapon) so powerful that no one wants to wage war with him. Interestingly, a similar expression is used about God (Exodus 15:8-11-18 and Micah 7:14-18-20).