President Truman had a sign on his desk which said "the buck stops here", and with good reason.
There is no excuse for a Western country's leader not to know what his or her government is doing in important areas, or to claim not to know. They have a personal staff whom they can personally choose, and is as many people as they like. A thousand people if they want.
As for being deliberately deceived, they have immensely powerful tools at their fingertips, right up to nuclear options like the ability to replace the head of any government organisation, launch an inquiry into it, abolish it or even, in Europe, pass legislation creating new criminal offences.