>>54,56
Flash was just "too much of a good thing". Originally it was a simple, efficient way to show vector graphics and animations with some little bit of interactivity. Then people started making websites consisting of exactly one page with a SWF on it, advertisers did you-know-what with it, and Adobe (not Macromedia) began bloating up the plugin with all sorts of extra bullshit.
It's better than JS because it isn't present in the browser all the time and only loaded when needed, and you can change it separately from the browser. That actually follows the UNIX philosophy of designed to do one thing well.