Destroyed itself? I can't say that's accurate except under the most restrictive definitions.
But I get what you mean, so
The non standard encryption combined with it being opt in. That decision made it a no go as a proper option for privacy and/or security purposes, and it was originally trying to edge into the whatsapp Facebook messenger market where it was already an uphill battle.
So it never took off the way it needed to in order to be almost unassailable.
Don't get me wrong, I use it and like it, for a given range of uses and a given value of like. But it just isn't a good replacement for much of anything at all. Yeah, features wise, it's nice, but not better than something like whatsapp. And it can't hang with any of the properly encrypted options. So you're left with something that's going to draw attention, but not the good attention. This makes mainstream users mistrust it, which rescues utility overall.