The M8, was not a one hit wonder. It was a phone developed with taking into account the feedback on the M7 and they did that marvellous. Personally I really dislike the black bar on the front of the phone with the HTC logo and not that much into the quality of external speakers but apart from that the M8 delivered.
What is mindblowing is this article holding on to the idea the M9 failed solely due too demanding expectations of the public. When Samsung released the S5 it was crushed for using the same design language and minimal upgrades even though the phone was actually better than the S4 even with its minimal upgrades and uninspiring design.

Now HTC made that same mistake with the M9. A third iteration of the same design used on the M7, a battery performing less good than the M8, a screen that also was of less quality like the M8 even though the specs of it were the same and a high MP camera which took disappointing photos so is it really the issue the public expected too much or is it just too hard to admit HTC really screwed up with the M9, relying too much on the praised metallic design and boomspeakers while the incremental upgrades didn’t offer any improvements and in fact performed less than the M8? And I am not even mentioning the issues with the 810 SoC which aren’t HTC’s fault but it made the public hesitant too.

No, let us admit, let us be honest. The M9 is not a good phone even though its specs suggest otherwise and public expectations aren’t the reason why it didn’t sell. Samsung learned the hard way and now HTC did even though Samsung still released a S5 which was better than the S4. Something HTC can’t say about the M9 compared to M8 if leaving raw SoC power out of the equation