Giardi has a pretty extensive take here:
Giardi: Malcolm Butler Benching Was "Culmination Of Events"
Excerpts that were of interest to me:
The missed flight doesn't sound like anything that was on him.
As most people assumed he was dressed as an emergency player that would only hit the field if absolutely necessary. If Jonathan Jones was still healthy there was a good chance Butler is inactive.
Weed is still in play but no clear confirmation yet.
Not only did he miss curfew he also brought "someone" back to his room. Both are no tolerance things. This kinda meshes well with that odd Reiss article from summer where he emphasized vaguely that most other players on the team are married with children.
It seems like the tight lips at Foxboro have held back quite a lot of things Butler was up to throughout his stay here. And it all came together in one big bang in his final game because he could not maintain himself during SB week for a few more days.