What challenge is the Trump administration facing from the federal government structure?

According to Elon Musk, the Trump administration is confronting significant resistance from an unelected federal bureaucracy. Musk states they've discovered there's a vast federal bureaucracy that is 'implacably opposed' to both the President and his cabinet. This opposition from career bureaucrats who weren't elected by voters presents a substantial obstacle to implementing the administration's agenda and improving government efficiency. The resistance appears to be systematic and entrenched within the federal government structure.