Earth potential and grounding
In a TT system the impedance between supply ground rod and local load ground rod is never going to be zero ohms so there will always be a voltage between the two when current flows. With a live fault to local load ground, current will circulate back to the supply star-point via earth.

There is nothing magical about ground that allows it to soak up current - a closed loop is needed for current to flow and the ground/earth is part of that loop.