When the theme returns, it is not alone.
Variants of this theme return throughout the 3rd and 4th movements.
The chords of the first theme return to close the exposition.
When the main theme returns for the first time, it has combined with the triplet pattern of the previous section.
The theme returns and eventually a climax is reached.
The movement then returns to F major, and the first theme returns.
The chorus then dies out, and the opening trumpet theme returns.
Mozart's purpose was perhaps to create a sense of variety by not having the main theme return at such regular intervals.
The first theme returns and is followed by a short coda.
After a dramatic middle section, the first theme returns and the work moves toward its conclusion.