The thing is, people did talk about how different Ryu looked in Street Fighter after SFII became a mega hit and they asked "if it's called SFII, does that mean there was a SF 1?" So when they decided to do a prequel instead of SFIII, they filled in lots of blanks and backstories.
Remember, this is an industry that felt the need to change the profession of Jumpman from carpenter to plumber after pipes became involved and actually developed a story for Pac Man.