Because Trump and his people are an insurgent force who have just executed a hostile takeover of the government, which is infested from top to bottom with sworn enemies of the republic.
It's going to take a while for them to gain control of every agency and department. It's akin to fighting house to house in a war zone.
You’re right, Rome wasn’t built in a day but, if ever there was a job for Kushner it’d be going to each agency and finding out what they’re working on and telling them what to drop, immediately.