It's easy to forget how popular flash was in that decade. A lot of us found it annoying on desktops too. Not to mention Linux, where we'd deal with binary blobs that were pretty unstable, not because we liked it but because you needed it to interact with the world.

I have not so pleasant memories of having a few different versions of their plugin and I'd try to figure out which one worked for a given website, symlink the right one and restart the browser. And that was the way to watch videos online...