Albert Barnes Commentary 2 Kings 13:6

"Nevertheless they departed not from the sins of the house of Jeroboam, wherewith he made Israel to sin, but walked therein: and there remained the Asherah also in Samaria.)" — 2 Kings 13:6 (ASV)

But walked in it — Rather, “he walked in it,” meaning Joash, the “savior” of the preceding verse.

There remained the grove also in Samaria — It seems strange that Jehu had not destroyed this when he abolished the worship of Baal (2 Kings 10:26–28). Perhaps the “grove,” or Asherah worship, was too closely connected with the old worship in the high places to be set aside with the same ease as the rites newly introduced from Phoenicia.