I feel like flash could have been adapted to low battery quite easily (it isn't like JS has some super smart concurrency; it is literally the basic common denominator unless you are using a Z80). Rather, Macromedia was in the toilet, then purchased, and Youtube (and Vimeo and others) started to be useful, making a more appealing platform (and probably the first other than newgrounds) for animation. Having someone else host media was a big +++