YOU SAID:
Zamasu killed all mortals because he could.
INTO JAPANESE
Zamasuは彼がすることができたのですべての人間を殺した。
BACK INTO ENGLISH
Zamasu killed all humans because he could do it.
INTO JAPANESE
彼がそれをすることができたのでZamasuはすべての人間を殺しました。
BACK INTO ENGLISH
Zamasu killed all humans because he could do it.
That didn't even make that much sense in English.