On a related note, who came up with the hand actions for football? And why are so many of them the same??

I can not speak to who created specific signals, but the origin of using hand signals in general stems from the growth in popularity of these sports among spectators. In large venues, and with a non-expert public watching, it was necessary to have some way to indicate what had occurred so that the spectators would understand. There were no PA play-by-play announcers or wireless ref microphones to communicate verbally what was occurring.

For Football, this came about in the 1920s - here's a solid magazine article on the subject that provides some photos: http://www.oldmagazinearticles.com/football_referee_signals_history_pdf

As far as the signals themselves, I'd say (for football) that over half of them are pretty self-evident what is being referenced. Motions akin to shoving people, to hitting them, to the direction the ball is moving, to hitting the ground, to tripping or blocking in the legs, all match the penalties they reference. Some of the signals used today date to the 1920s and can be seen in the article linked above - others have changed for whatever reason in time since. It's entirely possible (and this is speculation - be advised) that some simply were chosen because they are a big obvious action that was different from other signals already in use, and so could be chosen to communicate abstract concepts like "ineligible receiver" or "loss of down."