1)
Why is this verse here?
1.
Radak #1: It refers to verse 8; it discusses creation of the world. Malbim - this is why all should fear Him. Also the land standing is not automatic, the way Shamayim stands automatically from the nature that Hashem put in it. Rather, Hashem made sand a border for the sea and gives the rains in their times (based on Yirmeyah 5:22, 24). All must fear His punishment, lest He remove His Hashgachah for a moment, and all will die and return to the earth.
2.
Radak #2: It refers to verse 10. Since He created the world, everything is in His hand. He annuls nations' counsel; man cannot change what He commands to be, via strength, wealth or strategies.
