There were several factors that caused the demise of the Palm/HP phones.  Palm did not have the capital reserves needed to do the proper promotion.  The phones consistently won awards for novel features, still being copied today.  When HP bought Palm, it looked like their bad days were behind them.  However, Verizon systematically steered customers that wanted the Pre Plus to an Android phone.  They would badmouth both the Pre and the iPhone (which wasn't available on Verizon yet) at the same time that the technical press claimed it as the top smart phone.  Verizon then made a deal with HP for the Pre 3, but then canceled the order the week before it was to ship.  One month later the CEO, Leo Apotheker, killed HPs phone and tablet business and wanted to shut down the PC division.  Leo has the distinct reputation of being the worst CEO of HP, even worse than Carly Forina for this decision.

So, the decision to kill the Pre phone was a combination of the stupidity of a CEO that had no place running a company like HP and Verizon's help by refusing to partner with HP/Palm.

http://www.intomobile.com/2011/08/18/memoriam-life-and-death-webos/

It's interesting to note that the Palm/HP designers were immediately scarfed up by Apple, Google, LG, and others.  I don't know of a WebOS designer that didn't have a new position within a month of the shutdown.  In fact, the Nougat project was driven by one of the WebOS principal designers.  LG released a WebOS TV that has won top awards for usability for 4 years in a row.

Saying that the death of Blackberry is inevitable is disingenuous as BB has a lot more cash reserves than Palm ever had and their software thrust has turned around the negative cash flow.  They are not out of the phone business, but are outsourcing design and manufacturing.  A BB phone with a PKB is expected next year (pictures are already leaking).

It is sad that Verizon wields enough power to make or break a phone (except in the rare case with the iPhone). This limits choices and allows inferior products to flourish while stifling new and novel devices.  Even today, an unlocked BYOD will likely have features disabled when you plug in a Verizon sim.  Whether you think that one device is better than another is a subjective choice that the market should decide, not the carrier.