I would say Ovechkin is a good leader for how he conducts his play on the ice, but I would appoint somebody else as captain if someone could do a better job. Unfortunately, the Caps don't have tons of experienced players or leaders. Maybe Knuble is one but he hasn't been there for long. Perhaps Poti would be a better choice, I don't know.
The Caps did choke, but having only one and a half goalscoring line (I give some credit to their second line) is really the bigger issue. They had little production from the 3rd and 4th lines all year and they certainly didn't get any help against the Habs. And yeah, Semin didn't show up either.
Ovechkin carried the team throughout the season and during this series so I don't understand why folks can blame him. He has no help.