"Rejoice over her, O heaven" (18:20). Why is heaven told to rejoice over her?

Here is what the chapter says. The verse reads, "“Rejoice over her, O heaven, you saints, apostles, and prophets, for God has judged your judgment on her.”" (18:20). It names those it calls to rejoice: "O heaven, you saints, apostles, and prophets" (18:20). And it gives its reason, beginning with for: "for God has judged your judgment on her" (18:20). The verses before it tell of weeping, and they give reasons too. "The merchants of the earth weep and mourn over her, for no one buys their merchandise any more" (18:11). Those who gain their living by sea cry, "weeping and mourning" (18:19), over "the great city, in which all who had their ships in the sea were made rich by reason of her great wealth!" (18:19). The words over her stand in both 18:11 and 18:20: the chapter has weeping over her and rejoicing over her, and it gives each its own reason. These notes explain "God has judged your judgment on her" (18:20) no further than its words.