1)
Why does it say "Kol Yamav Asher Horahu Yehoyada ha'Kohen?
1.
Rashi (from Divrei ha'Yamim II, 24:17, Shemos Rabah 8:2): After Yehoyada died, officers of Yehudah came to bow to Yo'ash and made him a god. They said, one who enters Kodesh ha'Kodoshim for a moment is in danger of dying. You hid there for six years! You are worthy to be a god! The king heeded them.
2.
Radak: As long as Yehoyada lived, he instructed Yo'ash and he did properly.
3.
Malbim: Horahu means that he ruled for him [in particular cases], but he was not Melamed him (teach him the proper path to go on). Therefore, after he died, Yo'ash veered from the proper path.
