It's clear from the other person's responses that they don't mean it as a jab (which you seem to have taken it to be). Many people have a mythical idea of needing to be a superhuman developer to get any position at a big name tech company. Reading this seems to have made this person realize that such positions might be not as out of reach as they assumed, and they were expressing surprise about that.
If I offered internships I think I'd be lucky to get a few applicants, but I thought internships at top tech companies like Mozilla were very competitive.
And why are you assuming that I wasn't qualified or a competitive candidate? I said I applied on a whim and wasn't drawn to Mozilla for any particular reason, not that I didn't deserve the job?
I'm only reading what you wrote: "I had taken one Android class, knew some Java". I guess I would have expected them to want some related open source work, or a lot of related coursework, things like that.