Yes and no. Ovechkin gave Crosby a two-handed high-stick slash just as he was about to unload the shot. The 'slew-foot' happened just as the goalie poke-checked Crosby and would've been a dubious call, in that it didn't take Crosby's leg out from under him. However Crosby's balance was affected and that worked against him when he collided with Niskanen. His head was lower and took Niskanen's waist-high stick full on.  Niskanen did not thrust the stick forward. The closing speed between the two players could've been 50kph or more.

The entire sequence, from when Ovechkin first made contact with Crosby until the collision with Niskanen, lasted about 1.5 seconds.

Ovechkin's initial high-stick slash was egregious, worthy of a game misconduct in my opinion. But it made no difference to Crosby's shot, because he'd been poke-checked by the goalie. Everything after that was just goal-mouth playoff hockey. Tough break for Crosby and the Pens, but nothing to get too worked up about.