And conversely, to have apps you need developer buy-in, and to get that you need to demonstrate potential for wide adoption or be so intriguing that devs want to build for your platform regardless.

This is where starting low-end hurt. As noted by others, this made it difficult for Firefox OS to perform well in users’ hands, but additionally the users willing to take a risk on a new platform generally aren’t usually the ones who are interested in low-end hardware. People buying cheap phones primarily want a high value proven workhorses, and anything running an experimental OS is the opposite of that.

As a result, buzz around the project was minimal and quickly dissipated. Devs weren’t excited about it and didn’t talk about it and thus didn’t develop for it.