I am no expert here but why did Damien not get more snaps?

Because he didn't need to.

Same reason Derrick Henry had less than 100 yards vs. every low level team in 2015.

Harris will have his time to shine vs. bigger fish, and this gave an opportunity to feed Najee.

No reason to run a guy that you already know what they can do in a game that is already in hand. Damien will be getting plenty of carries in important game.s

On the subject of "The hot hand," I think different backs are more/less effective depending on the opponent's personnel. For example, we've always had a back that could really take it to LSU, but maybe didn't look so good vs. other teams for whatever reason. Or like that Sugar Bowl when Oklahoma had no answer for Derrick Henry.
Obviously there were times in 2016 when Bo should've gotten every damn carry

I think you see how effective the backs are against that particular defense, and then go ahead and give them 80% if they're dominating.
I don't think it's some mysterious "hot hand" thing as much as I think it's about specific personnel matchups