For many years, Flash has been the way to enjoy video on the Internet. It's low data usage (for video anyway) make it ideal. One could also create interactive Flash Apps that could be used for games or other functions.
But the fate of the Flash technology was probably sealed back in 2005 when Adobe acquired Macromedia. Adobe, in my opinion, is one of the greediest and least cooperative companies in the IT world (and that is saying something). One of the biggest uses of Flash technology came to be intrusive video advertising that would disrupt a web site reader who was simply trying to read an article quietly. Further, Adobe failed to maintain security and stability standards that created problems for the computer user.
Steve Jobs refused to incorporate flash into IOS, meaning flash could not run on iPhones or iPads. Apple also stopped bundling Flash with new Macs in 2010, meaning users would have to download it separately. Apple claimed to be doing this for performance, stability, and security reasons. You can read Jobs' 2010 memo here.
Technical issues may have been part of the reason, but Jobs had no love for Adobe. He felt they had screwed him several times in the past. One was over postscript fonts. In the 1980's early Apple computers use Adobe's PostScript Fonts. This gave Apple computers a huge advantage over PCs for anyone who wanted to do desktop publishing. But Adobe refused to lower licensing fees as the market grew. This essentially forced it to become a niche product and greatly limited the growth of Apple.
Many years later in the late 1990's Jobs returned to a dying Apple, with a mission to resurrect the company. To do this, he needed to make sure software would be available for all sorts of functions on the new Macs. Jobs believed he had received an assurance from Adobe that it would develop a Mac version of its video editing software. Then, suddenly, Adobe changed its mind after deciding that the Apple market would never grow big enough. This greatly upset Jobs who then had to spend a few years developing a decent video editing program in-house.
So by 2010 when Adobe was facing tougher competition and Apple was ascendant again, Jobs was more than happy to find a reason to stick it to Adobe. Flash made up 75% of all online animation at the time. People thought Jobs was crazy. But with HTML5 taking a more prominent role, more animation, video, and interactivity could be done without Flash. More and more companies have been dumping Flash, as it continues to slump toward irrelevance. Youtube has stopped using it. Even the browser Firefox has been trying to eliminate it.
Oddly enough, I will miss Flash. Don't get me wrong, I have found it quite annoying over the years. But the big benefit of flash over HTML5 over the past few years was that Flash was a separate plug-in. That meant that I could choose not to plug it in, or could use a simply flash blocker program to prevent being attacked by flash based ads or other nuisance video. The move to HTML5 makes it much harder to block these annoying intrusions as they are much more tightly woven into the fabric of the page itself. As such, I find myself subject to much more annoying ads, videos, and noise when I simply want to read a text article. I'm sure I will find a way to block this nonsense eventually. But with the end of Flash, I feel like I am starting my battle against advertisers all over again from scratch.