Change, no matter how seemingly minor, will bring some level of hope to a fanbase. It's normal that die hards like posters around here will take a small tinkering like a secondary's coach and build it up as a game changer. This is no different than any other fanbase.
When you have a franchise as dormant as this has been for over a generation now, and especially with the winning tradition this one has, the desire for change will be overwhelming. So when a fanbase is stuck with the same HC for a decade with the franchise going nowhere, the desire for change must be expected.
If the results from MM is no better than Garrett, I'm sure you will enjoy bringing back threads of this fanbase and their excitment for change. But that doesn't make the firing of Garrett and the hiring of McCarthy the wrong move.
The Cowboys can finish 2-14, and getting rid of Garrett would still be the right move