My dad was one of the many tracking specialists for the MSFN. NASA tracked Apollo via the global Manned Space Flight Network using Unified S-Band radio ranging and Doppler shifts for precise real-time position and velocity. Onboard inertial systems and optical sextant sightings provided independent verification. This multi-layered tracking enabled accurate translunar trajectories and midcourse corrections, impossible without actual spaceflight.
Faking it across dozens, 29 ground tracking stations, 4 ships & 8 aircraft of global sites with precise, cross-verified physics (impossible to simulate perfectly from Earth) makes a hoax vastly more complex than actually flying the mission.