Here's why:
* The "e" at the end of "credit" is silent. This means the vowel sound comes from the "i" in "credit."
* The "i" in "credit" isn't a short "i" sound like in "bit" or "sit." It's a longer, gliding sound that starts with a sound similar to the "i" in "machine" and glides towards the "e" in "bet."
So, the vowel sound in "credit" is closer to the sound in "freight" or "height."