He cut the ponytail off and ended up with the equivalent of a front comb-over\back as most of his hair at the back was gone already. Sorta similar to what Herr Trump does with hair from different parts of the head gown long so it can partially cover balding areas.
Sorta surprised he never went the implant route, he has enough on the sides and lower down the back of his head to thicken the top , in the pics above you can tell how thin on top he is.