The Huffington Post wrote, "State Department officials say Rudy Giuliani’s foreign policy backchannel 'undercut' U.S. policy on Ukraine." And Ambassador Taylor testified, "The official foreign policy of the United States was undercut by the irregular efforts led by Rudy Giuliani."
There must be some confusion. Under the U.S. Constitution, it is the president of the United States who determines foreign policy. How can President Trump be "at odds with foreign policy" when he's the one who determines it?
President Trump may well have been altering foreign policy on Ukraine. It should be of no surprise that he wasn't operating "business as usual," since he ran on that platform and has executed it from day one.
It's clear that Kent and Taylor didn't like or agree with Trump’s ideas, and believe they know what’s best. Trump rankled, contradicted and “embarrassed” them by operating outside the "regular" chain. But they seem to miss the fact that their desires are subordinate to the president's.
"Official foreign policy," as they called it, is not an independent unmovable-force object that exists outside the president’s authority; it is what the president determines it to be. The diplomats must execute the president's wishes or resign from their posts if they feel they cannot bring themselves to do so.