Here's why:
* Short "a" sound: The "a" in "safe" makes a short vowel sound, similar to the "a" in "cat".
* "e" at the end: The "e" at the end of "safe" is a silent "e" that makes the preceding vowel ("a") long.
Therefore, while the "e" influences the sound of the "a," the "a" itself is a short vowel.