I think it's because Newcastle were a promoted team, and Burnley have done well that people forget how everyone thought this season would go. Look at pretty much any journalist prediction about this season from August, look at any prediction thread on here. Burnley are consistently the team who are predicted to go down the most.
ESPN: 13/18* pick Burnley to go down, 0/18 pick Newcastle
Mirror: 6/10* pick Burnley, 3/10 pick Newcastle
Independent: 6/10* pick Burnley, 3/10 pick Newcastle
Talksport: Burnley 2nd most likely, Newcastle 6th
BBC: Burnley in 17th, Newcastle in 11th
/r/soccer: Prediction thread, Burnley selected by more users than any other team. Newcastle are nowhere near
I understand that Newcastle and Rafa have done well, but Burnley were predicted to do a lot worse, and have ended up doing a lot better. Because of this, Dyche's only competition for Manager of the season is Pep (who will probably win it).