@Aerovistae Your english translation seems correct to me.

Starting a sentence with "À qui" does seem a bit weird indeed, but it's a construct that comes up most notably in some idioms

For example "à qui veut l'entendre", which literally means "to anyone who wants to listen (to it)"

"à qui" here really just means "Someon"

You could replace "À qui s'étonnerait" by "Pour quelqu'un qui s'étonnerait"

the "ce que" is the other bit that confuses me

i think maybe i should make a question out of that

s'étonner de ce qu'il...