You're right, we're all speculating with the benefit of hindsight. Probably no one at Mozilla thought they'd spend three just to get something that could honestly replace Netscape 4. (This has suddenly become a Software Quality Rant.)
I would like to see programmers give up the idea that the only way to understand code is to rewrite it. It's nice that new programmers have the energy and inclination to start things from scratch, but we all know where the elephants go to die .
Maybe I'm going too far, but I doubt we'll see quality software until programmers learn how to improve *existing* software. Part of that means writing maintainable software, yes. Ovid's got it exactly right, above.
But if they only know how to rewrite, not maintain, there's little hope of that.