Keil & Delitzsch

The tyrants who usurped the rule over Israel have now utterly disappeared. "Dead men live not again, shades do not rise again: so hast Thou visited and destroyed them, and caused all their memory to perish." The meaning is not that Jehovah had put them to death because there was no resurrection at all after death; for, as we shall see further on, the prophet was acquainted with such a resurrection. In mēthim (dead men) and rephâ'im (shades) he had directly in mind the oppressors of Israel, who had been thrust down into the region of the shades (like the king of Babylon in chapter 14), so that there was no possibility of their being raised up or setting themselves up again. The לכן is not argumentative (which would be very freezing in this highly lyrical connection), but introduces what must have occurred eo ipso when the other had taken place (it corresponds to the Greek ἄρα, and is used here in the same way as in Isa 61:7; Jer 5:2; Jer 2:33; Zac 11:7; Job 34:25; Job 42:3). They had fallen irrevocably into Sheol (Psa 49:15), and consequently God had swept them away, so that not even their name was perpetuated.