The Quran reserves malik for flawed or equivocal mortal rulers

Evidence

In both Qur’an and hadith the word malik is sometimes used as a divine epithet, in which case of course it has a positive meaning. As applied to mortals, it often carries a connotation of presumption and even of paganism. Both David and Solomon appear in the Qur’an and both are positively portrayed. But both are prophets and, though depicted in royal splendor, are not designated by the word malik. The only one of the ancient Israelite kings expressly designated as such in the Qur’an is Saul, in the Qur’anic version called Talut, and he has the same rather equivocal image in the Qur’an as in the Book of Samuel. — Bernard Lewis, From Babel to Dragomans, 526