Because Rehoboam humbled himself, the anger of the LORD turned away from him, and He did not destroy him completely. Indeed, conditions were good in Judah.
KJV
And when he humbled himself, the wrath of the LORD turned from him, that he would not destroy [him] altogether: and also in Judah things went well.
ASV
And when he humbled himself, the wrath of Jehovah turned from him, so as not to destroy him altogether: and moreover in Judah there were good things found.