Why does it say "Ki Hikimu"?
Malbim: They should have learned Musar from Bnei Yonadav 1 - still, they did not listen.
Malbim himself (verses 2, 4) explained that Hashem commanded Yirmeyah to offer them to drink in a place that will publicize the matters. This implies that it was not known until now! (PF)