You're right; a similar thing happened (in quieter tones on this site) with the lead up to and election of, then early days of Obama. People love pinning their hopes and dreams on one person, but they shouldn't. Corbyn is not the Labour Party, nor is he the messiah. From what I can see there's nothing fantastic about labour because it's full of people who will do whatever it takes to keep their jobs, but never the right things.
A coward with good intentions isn't any different from a brute with bad ones for the people on the receiving end.