Word or phrase for something that turns out great but wasn't intended as such

I’m translating a German press release about a product that became a great tool/solution, but it had never been intended to be developed like that in the first place. It more or less happened by accident.^*

I came up with this translation:

Few developments that turn out to be good have been intended and meticulously planned from the start.

This is a rather literal translation, but it sounds quite awkward. Is there any idiom for something that turns out better than expected and wasn’t planned as such?

_{* For reference, in German, it’s “Nicht alle guten Entwicklungen waren von Anfang an beabsichtigt und penibel geplant. Auch die Initialzündung für XXX geschah mehr oder minder zufällig.”}