Why does it say "Ki Lo Yavinu El Pe'ulas Hashem"?
Radak: They do not engage in Avodas Hashem. They put to their hearts to understand only follies of this world; they contemplate and grow wise about them - "Chachamim Hem Lehara u'Leheitiv Lo Yada'u" (Yirmeyah 4:22). Understanding Hashem's acts is part of Avodas Hashem - science of nature and His acts in Shamayim and in the land. One contemplates that all is from Him; He is the first Cause. "V'Es Po'el Hashem Lo Yabitu u'Ma'ase Yadav Lo Ra'u" (Yeshayah 5:12) is one who does not calculate Tekufos (solstices and equinoxes) and Mazalos (when the constellations rise; this varies during the year) (Shabbos 75a). Since they do not try to understand Hashem's works, He should destroy their works.
Malbim: Refer to 28:4:1:1.
What is the tense of "Yehersem"?
Radak: It is a Tefilah - "Ten Lahem k'Fa'alam" (verse 4).
If He destroys them, surely He is not building them!
Radak: Do not build them after You destroy them.
Malbim: Make them think that You are building them, and really, You are destroying them.
