en_tn/2ch/34/05.md

he cut apart ... He broke ... He scattered ... He burned

Josiah would have commanded his workers to do these things. Alternate translation: "he had them cut apart ... He commanded them to break ... He had them scatter ... He commanded them to burn" (See: rc://en/ta/man/translate/figs-metonymy)

He burned the bones of their priests on their altars

This means that the bones of the priests who offered sacrifices on the altars to the false gods were burned on the altars that the priests had previously made sacrifices on.

he cleansed Judah and Jerusalem

This speaks of Josiah causing Judah and Jerusalem to be acceptable to Yahweh as if he made them physically clean. Alternate translation: "he caused Judah and Jerusalem to be acceptable again to Yahweh" (See: rc://en/ta/man/translate/figs-metaphor)