The issue at hand is trustworthiness, not who is better playing the game of leverage.
That is a dangerous game to play, particularly when you are Trump’s position.
Trump is leading our faithful patriots (which includes the military).
He will use every tool at his disposal...and that includes leverage over people in power (past and present).
If he thinks Kissinger has useful power or knowledge of any kind, he will avail himself to it.
If the key to that power or knowledge is leverage...then so be it.