When montag first meets the group of men by the fire, why is he surprised?

When Montag escapes he tries to float down the river until he gets to a part of it where a group of men whom to Montag´s surprise have memorized complete books. By doing this, the men can save the books orally while the law againts books could be overturned.  This is very difficult to Montag to comprehend that somebody can be so different from him, because he burns books for a living.

Nevertheless, this group of elderly men actually respect him, and were able to understand his motives and reasons to do what he did. At the same time, these were very educated men and completely opposite to him. they treasured books  rather than destroying them.

Granger, the leader of these educated men actually welcomes Montag back to society as a new man, after someone set up to look like Montag is killed, Granger allows Montag to be a new man completely change from the destruction he was accustomed to, and to join a life of thinking and awareness.    

its probably fingerprint or personality

it probably should so i can spam dank memes