In the heliocentric view, what causes the observed retrograde motion of planets like Mars?

Answer

Earth overtaking the slower-moving outer planet in its orbit

When the Sun is central, retrograde motion is a natural consequence of Earth overtaking an outer planet (or being overtaken by it) on its respective orbital path.

In the heliocentric view, what causes the observed retrograde motion of planets like Mars?
suntheoryuniverseorbitplanet