The idiom "followed the ... practices" means to do those things. Alternate translation: "they did the disgusting things that the nations did" (See: [[rc://en/ta/man/translate/figs-idiom]])
A place that is unfit to be used for God's purposes is spoken of as if it were physically dirty. The word "house" represents the temple. Alternate translation: "They polluted the temple of Yahweh" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-metonymy]])