Wally West had been around since the 50s, longer than most current comic book characters. Over that time, fans had seen him grow from Kid Flash to Flash, join the Justice League, get married, and have kids. In fact, by the time Flashpoint happened, Wally had been the Flash almost as long as his predecessor Barry Allen had been. And yet, for the first three years of the New 52, Wally was nowhere to be seen. Never even mentioned.
And then he was: in April 2014, in The Flash Annual #3, he finally showed up. Sorta:
Some fans argue that this isn't the real Wally West, just a new character that happens to have the same name. It's easy to see why: he has a different race, age personality, background, and costume than the Wally West people were asking for. No one can say for sure why DC decided to change the character so thoroughly, but one change CAN be explained.
See, around the time this issue was being made, they were also filming the pilot for the 2014 series The Flash. And in that pilot, Joe and Iris West look like this:
So they made Wally biracial to explain it.