Numenta's HTM theory seems functionally similar to variants of N-gram models (https://en.wikipedia.org/wiki/N-gram https://en.wikipedia.org/wiki/N-gram), where

Numenta's HTM theory seems functionally similar to variants of N-gram models (https://en.wikipedia.org/wiki/N-gram https://en.wikipedia.org/wiki/N-gram), where the model is able to predict future steps based on learned conditional probabilities. Maybe that's why it hasn't worked exceptionally well?