Flash did not disappear because of an unfortunate accident. It disappeared because Adobe was unwilling to fix its outdated system and rampant security flaws.

Anyone remember the flash-block plugins to keep browsers from auto rendering malicious flash content?

Jobs, 2010 https://www.webdesignmuseum.org/web-design-history/steve-job...

I did wonder why they didn't just switch out actionscript for js and use plain html/svg/canvas. I'm kind of glad they didn't but I think there would have been money in doing so.

Actually they did, Adobe still makes the Flash authoring tool but they call it Animate, it exports files that work with an HTML/JS player that does almost everything Flash did.

That was news to me!

Why we would do that when canvas related apis support gpu acceleration?

For the web you can now use Cocos2d-x[1], Godot Engine[2], PixiJS[3], and/or Phaser[4].

[1] https://www.cocos.com/en/cocos2d-x

[2] https://godotengine.org/

[3] https://pixijs.com/

[4] https://phaser.io/

Unity also has a very good pipeline for building webgl targets. You can virtually ignore the platform concern until the very end, as long as you aren't being ridiculous with real time lighting and texture resolution.