Albert Barnes Commentary Psalms 80:9

"Thou preparedst [room] before it, And it took deep root, and filled the land." — Psalms 80:9 (ASV)

You prepared room before it - The Hebrew word used here properly means to turn; to turn the back; then, to turn in order to look at anything; to look upon; to see; then, in Piel, to cause to turn away; to remove.

It then comes to mean to remove, or to clear from impediments so as to prepare a way (Isaiah 40:3; Isaiah 57:14; Isaiah 62:10; Malachi 3:1).

Consequently, it means to remove the impediments to planting a vine, etc.; namely, by clearing away the trees, brush, stones, etc. .

Here it means that the hindrances in planting the vine were taken out of the way; that is, God removed the pagan so that there was room then to establish his own people.

And did cause it to take deep root - Hebrew, “And did cause it to root roots;” that is, its roots struck deep into the soil, and the plant became firm.

And it filled the land - Its branches ran everywhere, so as to fill the whole land. See the notes at (Isaiah 16:8).