9:20 And the rest of mankind, who were not killed by these plagues, did not repent of the works of their hands, so as not to worship demons, and the idols of gold and of silver and of brass and of stone and of wood, which can neither see nor hear nor walk;

And the REST of MANKIND, who were not killed by these plagues,

With over 2 billion people dying after the fourth seal is broken and the sixth trumpet is blown, how will the remaining bury all the dead? Not only will this be a major health concern but the loss of this consumer power will reek havoc on the world's economies.

DID NOT REPENT of the works of their HANDS,

It is very interesting that the convincing done by MOUTH by the demons in verse 18 is translated in to real action in this verse. So convincing is the New Age fatalism, 'In me, I trust' or 'I can find my own God inside me, because I made myself the moralistic judge of my activities' that THE REST of MANKIND do not repent.

Under the seals, the people left recognized that they had suffered the judgment of God (Revelation 6:16-17). Here, there is not even recognition of God's judgment. They are so into self and idol worship as we shall see!

so as not to WORSHIP demons, and

This is especially abominal to God. Demons are created beings (by God) who have fallen (Romans 1:24-25). Don't worship the created; SERVE the CREATOR!

Note what the Bible says

Satan worship and demon reverence is ever growing. At this time, it is so prevalent, that it is the norm to do so. How else will the AntiChrist be worshipped in such complete subjection, and taking the "666" is accepted as a requirement by governments or coerced by 'strongmen'?

the idols of gold and of silver and of brass and of stone and of wood,

Paul in Athens argues the difference between God and the idols listed above in Acts 17:22-29-31. Check out this list again:

IDOL USE
Gold rule or authority
Silver medium of exchange (30 pieces of silver)
Bronze transportation (Revelation 1:15)
Stone strength or foundation (Matthew 16:18 and Mark 12:10-11)
Wood consumed sacrifices or human endeavors (1 Corinthians 3:10-12-15)

Even though all these things are either a poor imitation or outright fake, these people still believed these idols had some powers. This partially fulfills the prophesy in Zephaniah 1:14-18.

which can neither see nor hear nor walk;

Note this list leaves out speaking because idols do speak later in Revelation 13:15 as the image of the beast. However, speaking and additional attributes are given to idols in Psalm 115:1-8.

Attribute References
See Jeremiah 5:18-21-31; Ezekiel 12:8-16
Hear Jeremiah 5:18-21-31; Revelation 2:7; 2:11; 2:17; 2:29; 3:6; 3:13; and 3:22
Walk Romans 6:4; 2 Corinthians 5:5-10; Ephesians 4:1-6; Colossians 1:9-10-14; 1 John 1:5-7-10; 1 John 2:4-6-11.

Idols know better than to move when they are in darkness!