Albert Barnes Commentary 2 Kings 17:29

"Howbeit every nation made gods of their own, and put them in the houses of the high places which the Samaritans had made, every nation in their cities wherein they dwelt." — 2 Kings 17:29 (ASV)

The “Samaritans” here are the Israelites. The temples they built at the high places (1 Kings 12:31; 1 Kings 13:32) had remained standing at the time of their departure. They were now occupied by the newcomers, who set up their own worship in the old sanctuaries.