you know what to do

¹⁴ Then the five men who had spied out the land of Laish said to their brothers, "Do you know that one of these houses has an ephod, other household gods, a carved image and a cast idol? Now you know what to do."

When they said 'now you know what to do' it seemed like they were going to purge this household of false practices and idols but what do they do? They steal their idols AND priest and use them as centerfolds of their worship. Not exactly sure what the "lesson" is here but it does seem like worshipping practices were out of control.