What killed the brand was the huge discount they put on the 8* models that ended up in the hands of teenagers, remember that BlackBerry messenger was the one behind the London Riots.
The physical keyboard was really nice but the rest of the phones just weren’t. If they’d shipped a WebKit browser earlier it might have helped but they really hit a hubris-assisted low point floundering for years right when Apple and even Google started executing very well.
The best case might have been a Microsoft acquisition and doubling down on enterprise integration and features like the really nice one they added for locking down your work account from your personal data on the phone.