King Joash asks this rhetorical question to accuse Jehoiada of not doing his duty. It can be translated as a statement. AT: "You have neglected your duty. I told you to require the Levites ... covenant decrees, but you have not done it." (See: [[rc://en/ta/man/translate/figs-rquestion]])
Although it refers to the temple that Solomon built, it is a reminder that this tax has been collected since the time of Moses and the "tent of meeting."
# holy things
This refers to the items used for worship in the temple.
# to the Baals
"to people to use for the worship of idols of Baal"