source

Probably just based on a visual interpretation of the sounds, as abstract as that sounds. Could be wrong though.

it went from abstract drawings of things like animals to letters

That makes no sense. You only associate those letterforms with those sounds because you're already programmed to know how they correspond. If you were first creating the alphabet you would have no idea how to represent a sound like that, there's nothing telling you that B's sound "looks" like the letter B besides cultural programming

Also these letters hold literal power over us and are derived from occult-related s*** (Hebrew plays a big part I believe). There's a reason it's called "spelling" and "cursing"

well o was because it sounds like o

Well it had to come from somewhere.