Someone won the race. → Who won the race? (Ethan won.)
Something happened. → What happened?
Someone called you. → Who called you?
Not "Who did win the race?" — say "Who won the race?". Who 问的是赢的人，也就是动作发出者，所以不用 did：Who won?
试一试: Someone called you last night. 问动作的发出者。（省略不需要的词。） 答案: Who called you last night? — 你是在问打电话的人是谁，也就是动作发出者，所以不用 did，直接保留 called：Who called you last night? "Who did call" 多加了一个不需要的 did。
who 或 what 是动作承受者的时候
问动作的承受者（动作作用到的对象）时，要用 did + 动词原形，跟普通问句一样。
You called someone. → Who did you call? (I called Sofia.)
You saw something. → What did you see?
Ethan invited someone. → Who did Ethan invite?
Not "Who you called?" — say "Who did you call?". 这里 who 是动作承受者，所以要用 did + 动词原形：Who did you call?
试一试: Ethan invited someone to the party. 问动作的承受者。（省略不需要的词。） 答案: Who did Ethan invite? — 你是在问 Ethan 邀请了谁，也就是动作承受者，所以用 did + 动词原形：Who did Ethan invite? did 后面动词要用原形（invite，不是 "invited"）。
试一试: Someone broke the window. 你想问是谁做了这件事。把问句组建起来。（省略不需要的词。） 答案: Who broke the window? — 你在问是谁做的——也就是动作发出者——所以不用 did，直接保留 broke：Who broke the window? 如果问的是动作承受者，那才需要用 did。