The greeks adopted the phoenician alphabet, even though phonologically phoenician and greek languages have a lot of differences. I have read of a theory claiming that greeks simply misheard the sounds of the phoenicians and made the best adaptation for greek. So for example, alef [1] became a vowel in the greek alphabet, since the glottal consonant was not present in greek.

[1] - https://en.wikipedia.org/wiki/Aleph