I think the eye-poke moment was the turning point. Until that point in time both JJ and DC were gassing, but during that little break JJ seemed to have recovered while DC was still gassed.
DC probably went into the fight thinking that he was going to dominate Jon with his wrestling and defend all of Jon's takedowns and then Jon took him down in the first minute of the fight, which must have thrown DC off his game.
What do you guys think?
The pressure game only really works if you can force the fight into positions where you're able to rest and he has to work.
It wasn't just the one takedown. Every time Cormier got close Jones would end up in the better clinch positions where he was leaning on Cormier and resting. Jones made Cormier work harder, so it was Cormier that gassed first.