I have some possible theories on why the majority of Khan academy´s badges had suddenly been retired.
-The theory I originally had was that they had some issues with coding, and were going to remake the badges at a later time.
-The next theory was that the badges were going to be replaced by new badges to try to keep things fresh.
-The third, (but unlikely one) is that they removed the majority of the badges to keep thing simple.
I doubt that any of these might be the reason why, but we will find out eventually what the reason was.