John Gill Commentary 2 Kings 23:14

"And he brake in pieces the pillars, and cut down the Asherim, and filled their places with the bones of men." — 2 Kings 23:14 (ASV)

And he broke in pieces the images
Of Ashtoreth, Chemosh, and Milcom, in the above high places; which as these high places had been rebuilt by Manasseh or Amon, so new images of these deities were placed there:

and cut down the groves ;
in which they were set:

and filled their places with the bones of men ;
of idolatrous priests and worshippers, buried in parts adjacent; these he dug up and scattered in the high places and groves to defile them, bones of the dead being by law unclean, (Numbers 19:15) .