how和what 的用法有什么区别?

-How was it that you came home much earlier than usual?
为什么你今天回来的比往常早?
-Oh,a friend of mine offered me a lift.
哦,我的一个朋友载我的.
How 表示 程度,强调事情是如何发生的 ,而what 只是单纯的什么 ,如果用what 就不合逻辑了.
就像 how could you do this to me 你这么可以这样对我?如果改成what could you do this to me 就不通顺了.

这里 how was it 有 what happened/something must have happened so you came home much earlier ...的含义呢
How was it that you came home much earlier than usual? = How come you came home ... = Why did you ...