It's not easy to rebel in the Imperial Palace. Now, the Pingyang Palace is filled with Zhao Hanzhang's people, even the eunuchs and palace maids are carefully selected. She prefers quality over quantity, opting for personal guards to follow orders rather than using palace maids who cannot ensure safety.
Fu Tinghan is even more so, those who are not their people can't even see him; even walking in the palace, neither eunuchs nor palace maids come into contact with his men. The security level is beyond that of Zhao Hanzhang.
Ming Yu was ultimately persuaded by Zhao Hanzhang and Ji Yuan. They hit both ends; he's watching Liu Yi to prevent harm, while Ji Yuan sends spies to contact Liu Yi to gather intelligence on the Xiongnu secrets.
Not to mention, Ji Yuan really managed to plant someone inside.
