A reason why a Melech is: מ ְיודח ְ unique for Bitachon can be because a Melech is smeared with oil. He is “on top” like oil, and Bitachon means you’re “on top” of a situation, and you aren’t Nis'pael (impressed). The whole idea of Malchus is not being Nis'pael, since Hispa'alus means being “under” and impressed, which is a Shiflus and a lack of strength.
Notice how a lion (who is a king) is always “cool”; unaffected and unafraid. He is calm and relaxed, and is proud and “on top”. He is indeed super strong, and those who keep Sh’mita (Baalei Bitachon) are called גִּׂבֹּר יְכֹחַ ְְעֹשׂ יְְד ב רוְְֹתהליםְקגְכ “strong” ones, who do His command. (Medrash). Some say that: בּ רוךְְְהַ גֶּבֶרְ אֲשֶׁ רְ יִׂב טַ חְ בַּה'ְְירמיהְ יזְ ז is a Lashon of Gevura (strength).
My Rebbe told me that Bitachon and Ga'ava are similar. And just as Malchus/Bitachon means no fear of “people”, so does it mean no fear of life’s issues. The king is: מ ְיודח ְְְהמ ְח ְל ְמְִׂל ְ unique for war because he is strong.
