What is the meaning of "Hu Devar Hashem Asher Diber"?
Radak: "Hu" refers to above - Shalum killed him and ruled in place of him, like Hashem said. Whether he ruled a short or long time, Hashem's word was fulfilled. The kingship was transferred to others, for they were all Resha'im. Had they been good, their kingship would have lasted. Their kingship should have ceased earlier, due to their sins. Zecharyah ruled six months only to fulfill Hashem's word, so they will know that the Navi spoke Emes to Yehu in Hashem's name - "Bnei Reva'im Yeshvu Lecha Al Kisei Yisrael" (10:30).
Why does it say "va'Yhi Chen"?
Rashi: [Yehu']s kingship was not worthy to last so long, rather, to fulfill [Hashem's] word - "Ken Yihyeh Devari Asher Yetzei mi'Pi" (Yeshayah 55:11). Malbim - i.e. Hashem's word for good is not rescinded. Based on nature, they would have rebelled against him 1 , for [Shalum] killed Zecharyah in front of the people without fear. Rather, Devar Hashem caused Yehu's kingship to last until now.
The verse discusses Yehu, but it seems that Malbim refers to Zecharyah. Perhaps everyone hated Zecharyah, therefore Shalum did not fear to kill him openly. We cannot infer so about Yehu and the three generations between him and Zecharyah! (PF)
