It's definitely tactical, but perhaps others could be more precise about if/how the rules have changed to enhance this.
I suppose you might guess and say that the increased athletic profiles of the players has enabled them to get to more contests or to spoil more disposals.
I'm personally not a fan of the constant contest, I'd like to see a bit more freedom for players to play, but buggered if I know what steps you'd take to allow that to happen.
The answer lies in combating the thing you raised in your own post.
"the increased athletic profiles of the players has enabled them to get to more contests or to spoil more disposals"
So you need to address that in order to resolve the constant rolling maul. Possible options
1 increase the size of grounds
2 reduce the number of players
3 restrict areas that players can move in
4 speed up the flow of the game
Obviously 1 can't happen, personally don't like 3 (the "netball zone") so that leaves 2 & 4.
2 - I'd look at reducing the onfield numbers to 16 and reducing the numbers of interchange players and rotations allowed (say 2 interchange and a sub in case a player injured - max 40 rotations).
4 - remove the need to nominate ruckmen at ball ups and throw-ins. Only one player from each team is allowed to contest - any blocking that prevents one team from contesting is a free kick. Ball ups and throw ins to occur soon as the umpire has the ball. Also look at a automatic free kick against a third man in where the intent is just to hold up the play to ensure a stoppage.
If the coaches are quite happy to turn elite AFL into an under 10's style all-in rolling rugby maul, then the AFL have to act.