Shipping a 1366 by potato screen phone with an outdated version of Android, and an app store that was missing most apps.
AT&T could only push that pile of crap so far, they really did have their sales teams push it hard though. Very hard to convince a customer to get a Fire phone rather than a Galaxy S4, or even an S3.
They did court apps with AWS credits and things (at least they did for the one I was working on). I think they didn't realize (or plan for) the part where apps had dependencies on other Googley stuff. Can't just push the apk to Amazon too, if Amazon doesn't have a workalike maps api, etc.
When the Fire phone was on Fire sale, it was a pretty good value for users though. The launcher was weird, but you could smuggle Google Play store on it, and it had a good processor.