At its end it was not used much for vector animation as it was used as for playing video on the web.

But it had a reputation for being insecure, and for being slow — because it retained the ability to put vector animation on top of videos.

When HTML 5 was adopted with video playback tags (safer, faster, open), that killed it for web video.

Well, to me that is the same thing, because since it was proprietary, Steve Jobs and Apple could not control it (and maybe improve it and adopt to their standards) - so they rather threw it out. (not that apple had a problem with proprietary tools, justs with proprietary tools not under their control, in a vital position)

If the Flash player would have been open in a way, chromium/webkit is, with many top players working on it - it very likely would still be around and maybe even dominating, as it was way superior in terms of features and more importantly, it was not a mess to work with, like HTML still is.