I once heard from a Rosh Yeshiva who has a knack for history that in all probablity the Golem never exsisted.
But the STORY of the Golem most definently did exsist in the times of the Maharal.
The Maharal, in order to make the goyim scared of the Yidden, concocted and led everyone to believe that there was a Golem capable of doing all of these things to people who made problems for the Yidden of Prague. He allowed all the stories about the great Golem (who noone ever actually saw, but everyone knew someone who actually saw it) to continue and grow to help klal yisroel from our enemies.