Here's why:
* The "e" in "eagle" is followed by a consonant ("a"). When a vowel is followed by a consonant, it typically makes a short sound.
* The "e" is also in a closed syllable. A closed syllable is a syllable that ends in a consonant. This further reinforces the short vowel sound.
The "ea" combination in "eagle" doesn't make the long "e" sound like in words like "eat" or "see". It creates a unique short vowel sound similar to the "e" in "bed" or "ten".