Dovid saw goodness in his worst enemies, like Shaul, Avner, Shim'i ben Gera, and his wicked son, Avshalom. Shaul’s son, Ish-Boshes, was his competitor, yet Dovid killed the two people who assassinated him, and called Ish-Boshes a Tzaddik. (ש"בַדַיא). A true Melech sees good in everyone, and the Rambam calls a Melech the Lev of Klal Yisroel. We can suggest that in truth, Shaul was a true Melech who excels in Ayin Tova (we find him being super nice and forgiving to people who defamed him in the beginning of his reign) but the Ruach Ra’ah caused his Kin'ah.
Also, since Klal Yisroel asked for a Melech: לַֹשֶַּׁאַכ ַהוֹןגֶַּ “improperly”, to be: כ כָלַה גוֹי םַַש"אַחַהַ like all the Goyim, in turn they received an: לַֹשֶַּׁאַ כ ַהוֹןגֶַּ “improper” situation with Shaul. Shaul was not from the royal Shevet of Yehuda, and his name, Shaul, means “borrowed”; i.e., a “borrowed” temporary Malchus. Hashem, who is total truth and Rachamim, understood the true greatness of Shaul, so in his death, his body remained whole, like an Ayin Tova person.
