John Gill Commentary Psalms 78:57

"But turned back, and dealt treacherously like their fathers: They were turned aside like a deceitful bow." — Psalms 78:57 (ASV)

But turned back From God and his worship, apostatized from the true religion, and turned to idols:

and dealt unfaithfully, like their fathers in the wilderness; see (Psalms 78:8Psalms 78:36Psalms 78:37)

they were turned aside like a deceitful bow that promises well to carry the arrow right, but drops it at the feet of the archer; or carries it another way, so that it misses the mark, The Targum is, ``as a bow casting arrows;'' to the ground, and not to the mark; see (Hosea 7:16) or being too much stretched is suddenly broken, and kills the archer; or returns to its own nature; so Arama.