i reckon at half time Gawn and Grundy figured out they were a lot stronger than Ryan so just started to batter him. They then took over the ruck contests.
In the 1st half they were jumping with him and Samson played really well.
As you say, they clearly had a discussion at half time, and changed to jumping into Samson to knock him off balance. Worked a treat and they got well on top of him. Once he improves his physical and most importantly cores strength so its harder to knock him off balance, we will see more of what we saw in that 1st half against Melbourne.