Rabbi Roodyn

ו) הִגִּידוּ הַשָּׁמַיִם צִדְקוֹ וְרָאוּ כָל הָעַמִּים כְּבוֹדוֹ:

The heavens told His righteousness, and all the earth saw His glory.

Rav Hirsch explains this pasuk by saying that once all things that are evil have been destroyed, once the way to better insight has been paved in the hearts of those receptive to such teaching. This will come together with the melting away of the imposing grandeur of once-feared earthly powers before the majesty of the sole, true G-d.

At this point all the events that heaven has brought about on earth will have accomplished their purpose, namely to bring to the attention of men the ideal of Divine justice and for them to relate to that as fact. Then, all societies of mankind will behold His glory. In all that is and in all that is yet to be, in all the phenomena of nature and all the events of history, they will see nothing else but revelations of Hashem.