It was a case of people not picking up the proper coverage, it wasn't all on Komarov. When the Rags enter the zone they only have four guys. Panarin is covered by a defenseman, as it another forward in front of the net. There are two Rags near the blue line who are also covered by Koivula and Martin. Panarin circles behind the net and Leddy, who was covering him, let him go. Mayfield kept battling with his guy right in front of Varlamov. The fifth Rag player comes into the zone and receives the puck, wide open and that's where the confusion is. Koivula and Martin both have a guy up top, but Leddy isn't covering anyone and is on the same side of the ice as the puck, and Komarov isn't covering anyone but he's on the opposite side of the ice. Leddy steps up, the pass goes to Panarin on the far side and Komarov never even sees him. I'm guessing that Komarov thought Leddy had him, since the Isles play man on man in the defensive zone, and that Martin or Koivula were covering the wrong players and would shift. They didn't, and it left Komarov just standing there like a dope.
That doesn't absolve him of the misplay, but I understand why Panarin was left open. Komarov never even looks at him to know he's there.