Back when I was sixteen, I hung out with this kind of crowd and most of the usernames were about how dangerous/scary/bad the person was. I thought it would be funny to deliberately choose a username that was the exact opposite of all of that.
I have to admit I'm almost 42 years old and a native English speaker, and until just a few minutes ago I didn't actually know what "munificent" meant. I just looked it up, and based on the thoughtfulness of your comments here, I think it's an appropriate username.
Thirty years later, I'm still using it.