Amos 9

Amos 9:8

"Behold, the eyes of the Lord GOD are on the sinful kingdom,
And I will destroy it from the face of the earth;
Nevertheless, I will not totally destroy the house of Jacob,"
Declares the LORD.

God is aware of the sins of the Jews, and is giving justice for them.  He is going to destroy their nation, and wipe it from the map.  This is the result for any country that does not honor God, sooner or later.

However, He does not destroy the people completely.  He spares enough that they will be able to eventually rebuild.  They may have strayed from Him, but He remembers His promise to be His chosen people, even when they don't.

Amos 8

Amos 8:5

saying,
"When will the new moon be over,
So that we may sell grain,
And the sabbath, that we may open the wheat market,
To make the bushel smaller and the shekel bigger,
And to cheat with dishonest scales,

What a piece of work, to be this corrupt consciously?  It's one thing to not respect God's ordinances on holy days, and to be consumed by greed and the desire for profit.  But to be actively looking forward to cheating their fellow citizens?

With that kind of attitude, I'd agree with God that these people need a serious cleaning out.  The only way to fix someone that twisted is a major shock to the system, and I can only think of two types back then.  First would be a major financial crash due to famine, and the second a hostile invasion force.  God chose to do both, I believe.