Yeah, there's a bunch going on there. Could maybe call it the difference between "hunting" and "war". Humans are long since complete apex predators with enough offensive power when prepared that no game animal is an active threat. And hunting tends to be solo (even if you go with a group of friends it's for fun and maybe sharing information, not everyone shooting at the same thing out of necessity). But in the game at a high level it's "solider vs soldier", either side can get the other so teamwork, positioning, tactics and strategy (including tactical withdrawals to more favorable ground, ambushes etc) are critical. It's also clear he fell into the classic trap of being too good for his starting level in a mechanical way, which let him dominate when everyone else had low skills, but also meant he never grew any further. Essentially in the newbie tier it was his "hunting" albeit with "more dangerous prey", so he didn't have his mindset challenged. So once they advanced to the point where all the opponents had good enough mechanical skills to make up enough difference he hit a wall. Whereas a newbie who built themselves up organically in game would have a far harder path, but no preconceptions or crutches either.
Of course his IRL skills/thinking/patience/coolness under pressure/raw mechanical talent are very valuable and unique assets. But the coaching here is good, he recognized a different approach than normal was needed for a very different set of strengths and weaknesses.