The fact that vine as a name and at least some vines are still at least somewhat prevalent online, makes me think that vine literally was "already" the next big thing and twitter just completely misread the room.
yeah, people are still reconnecting with vine creators, on TikTok. You can see in the comments, a video came up on the user's feed and they were compelled enough to be like "are you so and so from vine!?" Vine was killed half a decade ago.
And YouTube. Some of the biggest commentary channels used to be Viners.
The fact that it was shut down when it was is testament to how badly Twitter misplayed their hand with it. Every single creator flocked to whatever platform would take them at the time.
I think it's a lot more likely that there are/were a horde of PMs there who thought it was a very dumb and short-sighted decision to shut it down at the time. In my experience, it's usually some high-ranking exec who makes confounding decisions through authority in big tech. Not so much the average IC PM who has to spend time understanding their users for their job.