Consider this one
Alice was eaten by that lion.
I am pretty sure it is both grammatical and idiomatic.
Consider this sentence
John ate his dinner.
I am 100% certain it is grammatical and idiomatic. How about this one?
The dinner was eaten by John.
I am also 100% certain it is grammatical. However, I am not so sure if it is idiomatic. Could someone please give a hint? Thanks in advance.
Note: I am aware the concept of active voice and passive voice, I just don't really understand the usage.
The examples are adapted Another post (What is "passive participle"?).