It's impossible for us to determine whether or not Chara really intended to do this, but I do believe that Chara should be held responsible for his actions. First, it was an act of interference as Pacioretty already dumped the puck and was out of the play, and second, Chara has severely injured a player due to this infraction.
It could have been a matter of timing, where Chara wanted to shove him into that section between the benches. However, there should still be further punishment since Chara is 100% ACCOUNTABLE for how he conducts himself on the ice. By giving Chara zilch in terms of punishment, the NHL is saying (to me, at least) that you aren't responsible for the well-being of your opponents and this is more an issue dealing with the environment (the "turnbuckle" and the hard ice). This was Chara's mistake and he really got off easy.
P.S. I love how he just passively skates away. Even I, a lifelong hater of the Habs, am left with a bitter taste in my mouth.