Why does it mention Mo'av's [previous] serenity?
Radak (10): Amidst haughtiness over its great serenity it did evil to Yisrael.
Malbim: This is why Hashem decreed that it be exiled.
What is the grammatical form of "Sha'anan"?
Radak: It is past tense, for there is a Patach under the Nun.
What is the meaning of "mi'Ne'urav"?
Metzudas David: From when it was a nation (its youth).
Malbim: [It never was frightened] from outside [and had internal serenity].
Why does it say "El Shemarav"?
Radak: This is like Al Shemarav. Mo'av is compared to wine that stands on its dregs - it is good wine. When wine is poured from Kli to Kli, its smell and taste depart 1 . Also Mo'av was not yet exiled, and stood serene in its land.
Malbim: The dregs remain in the first Kli. When wine is removed from its dregs, it loses some of its taste and smell, unlike wine that remains on its dregs. The Nimshal is, a nation that was exiled from place to place, it changes its customs and etiquette to those of the place it came to.
What is the meaning of "Lo Namar"?
Rashi: It did not vanish.
Radak: Depending on context, this can mean softness and weakness, like the Targum 'Lo Fag.' This is like "Al Ken Tafug Torah" (Chabakuk 1:4), "Al Titni Fugas Lach" (Eichah 2:18), "va'Yafag Libo" (Bereishis 45:26). Also Chazal said (Megilah 25b) 'perhaps Faiga the mindset of the Tzibur', i.e. it will weaken; 'the body is hard - wine is Mefigo' (Bava Basra 10a), i.e. weakens it. Also the Targum means that the wine's strength and smell did not weaken.