Mentally weak. Rus Fed needs to find someone else to get behind. He just can't cut it on the big stage.
You don't walk in Kovtun's shoes, so you really don't know what it could be about, anything from nerves, illness, injury, equipment problems, jet lag, personal family problems, coaching issues. Plus,Kovtun might have a lack of confidence in his performance skills which could have caused him to falter from pressure of skating in the last group with guys who clearly are better than him. I think Kovtun is a second tier skater anyway, as is Voronov, but simply the ability to land quads carries so much more weight than it should. The sport is so whacked, especially in the men's event.
It's not great of us fans to tear down skaters when they perform poorly, since they get enough tearing down by the judges, that is unless they are Yuzu Hanyu who gets lots of points, even when he's never skated two clean performances in his life. That's not a tear down by me, btw, it's simply a fact.
On the men's side, we by now should expect these kinds of mistake-ridden events with the quad taking so much out of these guys mentally and physically. The quad is over-rated. The sport should not be so heavily weighted toward acrobatics. What these guys do is tremendous by itself, even without quads. These programs are filled with so much difficult tech content, it's close to being inhuman what's required to be on the podium.
And looking at the detailed scoring breakdown, clearly Jason Brown is way lowballed on Performance Execution, Transitions, Choreo, and Interpretation. No way Sergei Voronov should be even slightly higher on PCS than Jason. The judges absolutely don't know how to analyze performance qualities. The PCS are used to bolster skaters with quads, and are generally meted out more stingily to skaters who don't have consistent quads.