My honest assessment, (having worked for a company that supplies parts and SW to Lab126 [1] in the past) is that the hardware design and specs were nailed down quite some time ago, but they took so long to execute and launch that the world they launched into was vastly different from the one they had targeting against when they first started designing the phone and coming up with the battle plans.
[1] Lab126 is Amazon's hardware arm that makes these phones.
[1] Lab126 is Amazon's hardware arm that makes these phones.