en_tn_lite_do_not_use/psa/078/037.md

their hearts were not firmly fixed on him

Here "hearts" is a metonym for their thoughts. To be loyal to him is spoken of as being solidly attached to him. Alternate translation: "their thoughts were not focused on him" or "they were not loyal to him" (See: rc://en/ta/man/jit/figs-idiom)