I can tell you where it fell off those lists.
1. Poor camera at launch. Huge screw up by Moto, especially for a flagship device with a flagship price tag attached to it.
2. High price tag. See #1. Reviewers were willing to trade the solid-performance-yet-not-top-of-the-line-spec for extended battery life, but couldn't overlook the top-of-the-line-price. Never mind the 32GB of memory, wireless charging, or novel voice controls.
3. The Ultra. In just about every Maxx review, it was either casted as the also-mentioned second player to the Ultra, or the Ultra was heavily referenced as the base model. Regardless, the general contempt the Ultra received cast a long shadow over the Maxx, when instead the comparisons should have been to the Moto X, and the and the Maxx should have otherwise stood alone.
Like it or not, the initial reviews crippled the Maxx as a serious contender for many potential purchasers, something no product can be expected to recover from.
I'm with you guys and the handful of people I've turned on to the Maxx -- Best Phone Ever (of 2013, that is).