Comment by Zigurd
This is not to take away from the corporate Vogon tragedy described in the blog post. WebOS could've been a credible competitor to iOS and Android. But the weak spot is right in the name: It's a web UI platform. Look at Google's attempts to make ChromeOS into a tablet OS.
While it's less clear cut now, back when HP acquired WebOS, they would've had to put in a lot of work to make WebOS competitive, and enable WebOS apps to work as well as iOS or Android apps. HP had the resources.
We don't have a third or fourth mobile platform mainly because of tragically poor leadership at HP and Nokia. Both were almost killed by CEOs who thought they were the corporate savior.
WebOS had a native development kit in addition to the web one.
They were way ahead of the game with stuff like wireless charging and the SoC was cutting-edge for its time with fast (1.2GHz, but the chip was designed to run at 1.5GHz and overclocking to 1.8-2GHz was not too hard) partially OoO dual cores and 128-bit SIMD instead of 64-bit like A9 paired with a good LCD. The UI as shipped was already ahead of its time and if you look around for the cancelled Mocha UI, I think it would look pretty modern even today.
The big issue is that they were a web-first platform, but their version of Webkit and JS JIT were years out of date which meant they were behind on web standards and WAY behind on JS performance at a time when JITs were still getting faster at a very rapid pace. The CPU was fast compared to everyone else, but it was still slow and they needed to focus on performance a bit more.