The Communist Party is relentless...
Spies everywhere...
Maybe I’m overstating it, but to have something like this happen means that a total flush of all SS agents and WH staff may be necessary...
That would either place the President at more risk or would have him holed up in the White House until the new staff could be trained... by whom? These movements are immense, involving complex equipment and teamwork, each member requiring intimate familiarity to reduce operations to muscle memory.
One doesn't stand up a new system overnight, much less than from zero.