The reason was that Takauji acknowledged Masashige's integrity and handed back the head of the fallen Masashige to his family in a polite way, saying that they must want to see him, although they might feel sad.
理由は、戦死した正成の首（頭部）を尊氏が「むなしくなっても家族はさぞや会いたかろう」と丁寧に遺族へ返還しているなど、尊氏自身が清廉な彼に一目置いていたためであろう。