To many people - To various nations using diverse languages.
Surely - The thought is that expressed by our Saviour Himself (margin reference). Some render it: “but I have sent thee unto these; they can hearken” etc.
Related Commentaries of Ezekiel 3:6
Ezekiel 3:6
6 Not to many people of a strange speech and of an hardb language, whose words thou canst not understand. Surely, had I sent thee to them, they would have hearkened unto thee.