Widely believed to be because Mike Bison was a little too on-the-nose for a heavyweight boxer and the shuffle was the easiest way to make a last minute change.

I also read that Capcom USA felt the name “Vega” was too “weak” for the dictator.

Someone already mentioned Mike Bison, but FWIW, in the fighting game community - which includes people from Japan and outside of Japan - those characters are generally called "Boxer", "Claw", and "Dictator" specifically because of the localization changes, to give them unambiguous names.

At least Sagat kept his name, though "Tiger bullshit" would've been a great moniker, and no, I'm not salty about losing to his projectile once too many.