The only person who is allowed to sit in the Bais Hamikdash is Malchus Bais Dovid. (Gemara). The Melech is the epitome of Kavod, and he is: מְְּׁיוּחְָׁד (singular) in that he can kill a person for not respecting him. Notice how in Dovid’s later years: בְּגָדִיםְׁ clothing couldn’t keep him warm, since he was once M'vazeh the clothing of Shaul.
This the last story of Dovid HaMelech. We can suggest that since the Gadlus of a Melech is his super high level of Kavod, therefore he was Niftar after being punished for being M'zalzel in clothing. Dovid was M'chabed everyone, especially his enemies. He kept calling Shaul: מְּשְִׁיחְְַׁׁה'ְְׁׁש"אְׁ כוְׁ ט-יאְׁ Moshiach Hashem (the anointed of Hashem), and his rebellious son, Avshalom, he called: בְּנִיְׁבְּנִיְְׁׁש"בְׁיטְׁא My son, my son, which is a Chashivus (a close relative needs to be respected).
And he called Avner and Ish Boshes Tzaddikim, even though they hadn’t really been on his side and were his adversities. Since a king’s main Tachlis is to be M'chabed, Dovid was Niftar after he was M'zalzel.
Dovid, the Admoni, goes Davka against his Eisav nature, and is not M'zalzel, like it says by Eisav: וַיִבֶזְׁ עֵשָוְׁאֶתְׁהַבְּכֹרָהְְׁׁכהְׁלדְׁ he despised the Bechora. And a Melech has the job to kill Amalek, who are known for their being M'zalzel in everything important and holy (like Kriyas Yam Suf. Chazal).
