Before I say anything: I am not a Muslim (although Islam is a religion I'm very interested in), so I'm basing anything I say here off of what I've read. If I'm wrong about something I apologize.
But in all honesty it's no different than Christians following Jesus & his teachings. And the Muslim community are not "following Muhammad". They are following God's will, which God chose to pass on to the masses through Muhammad.
Also Muhammad did not "start" Islam. Muslims believe Islam is the faith of Abraham, Moses, Jesus, etc., etc. Basically the same religion as Judaism & Christianity. Both started as Islam but went off track. The Qu'ran is the absolute, pure, untarnished "version" (for lack of a better word) to bring everything back where Jews and Christians might have gone astray.
As for "couldn't he have been wrong?". Sure but that's where the whole absolute belief/faith thing comes into play.