The problem was that in 2014, a $35 phone would get you specs worse than the original 2007 iPhone. Trying to run a mobile OS where the entire UI is written using web technologies on those specs basically made it unusable. Here's a review of one of the Firefox OS phones:
https://arstechnica.com/gadgets/2014/10/testing-a-35-firefox...Some choice quotes:
> If the lock screen pops up while reading a webpage, you'll need to reload the page again. If you start the stopwatch and leave the app, the stopwatch stops. You can set the e-mail app to check for mail every five minutes, but there is never any free memory, so the mail check never runs. There isn't even anything to keep the crucial alarm process alive. If the phone is busy when an alarm is supposed to go off, it just doesn't go off. An alarm you can't trust to work 100 percent of the time is useless.
> Typing on the Cloud FX is pure agony, and this is one of those really crippling deal breakers that makes the Cloud FX a bad phone at any price. The keyboard doesn't support multitouch, so you if press "Q" and "P" at the same time it splits the difference between the touch points and enters "Y." This means you can only ever carefully hunt and peck at a slow rate. It's very easy for the Cloud FX to slow down, so if anything is going on while you're trying to type, buttons will take a few moments to register. There's also no auto correction and no copy/paste.
> Navigating webpages is a nightmare. The problem isn't just that the phone is slow, it's that scrolling is nearly impossible. A lot of times the phone is busy, and scrolling doesn't do anything. When it does scroll, you'll find the rest of the page often isn't loaded and you'll get a gray screen that takes a few seconds to be loaded into memory. The other problem is that scrolling is often interpreted as pressing on a link. This, combined with the speed of the device and the often-frozen scrolling, means the Cloud FX is frequently doing things you don't want—and doing them very slowly.
> The performance of the Cloud FX really cannot be understated. Screen taps sometimes take seconds to register. Firefox OS has a recent apps screen, but there is never any free memory, so nothing other than the current app is ever open. During particularly slow freak-outs, the screen will just turn black. If the phone falls asleep, or the alarm pops up, or a phone call comes in, your app closes and you lose your progress. Even something as simple as opening a folder of apps has a load time measured in seconds.
> Getting devices out to the developing world will be a big focus for many OEMs, since the market is just so huge. There are billions of people out there that still need access to the Internet. We know we can't expect something so cheap to hold a candle to the high-end devices we normally review, but all we ask is that the device be executed well and that the decisions that went into the product make sense. The Cloud FX doesn't make any sense, though, even at $35. It doesn't seem like anyone set out to choose the best software for this device, and that was really the crippling decision. Low-end smartphones need a low-end-appropriate operating system, and Firefox OS isn't up to that task. We get the feeling there are relatively good, sub-$50 devices out there—but this isn't one of them.