I think Hypen is on the money with his interpretation.
The AFP has released a Strategic Plan for Sport-Related Concussion in Australian Football 2022-2026
here
it includes as a "Strategic Objective", "PREVENT Reduce the incidence of avoidable forceful head contact and SRC with interventions at each stage and level of participation in the game.
I was listening to David Mundy last night who opined that if it was a player like Scott Pendulbury attempting the smother, he would have used a different technique following the failed attempt that would have been much less likely to cause injury to Brayshaw than what occurred. Essentially Maynard could have put his hands out to protect himself and with much less risk of injury to Brayshaw.
Essentially Maynard used a more dangerous technique than was necessary. I think that is enough to satisfy that he was careless in his action. I don't think anybody is arguing the high contact, high outcome components of the charge.
There are plenty of sources available that promoting all sporting codes on educating players to use appropriate techniques when playing sport that mimimise the risk of causing the precise scenario that played out in the incident in question. Maynard's technique was one of self-preservation without regard to the risk it exposed others too. I think he has to wear the penalty.