As others commented on social media, it's probable that Lars heard these comments on the Oilers in a pre-game meeting, from his coaches, and his goof was in repeating them. It's the second example of Lars being a little goofy that I can remember, the prior one being when he was unaware that an opponent had made a goalie change during the game, he hadn't noticed the guy he was shooting at was different. So Lars may be a little scattered at times, he's not Guy Carbonneau or Jonathan Toews.
Michel Therrien did exactly the right thing when answering questions from the media, in saying that Lars had made a mistake and he'll learn from it. Nothing inflammatory about that. If he'd said that the Canadiens would have won if not for Lars' stupidity, then we could say he bungled it. As it is, his measured remarks were appropriate to the situation.
As far as whether he "threw Lars under the bus", that's off-base. Just so we're all clear, to 'throw someone under the bus' doesn't mean to rebuke someone, or to be mean to someone. What it strictly means is to unjustly blame someone (else) for something that's gone wrong.
To throw (someone) under the bus is an idiomatic phrase in American English meaning to sacrifice another person (often a friend or ally), who is usually not deserving of such treatment, out of malice or for personal gain.
The phrase has been widely popularized by sports journalists since 2004 and was picked up by the mainstream media during the 2008 primary season. It has frequently been used to describe various politicians distancing themselves from unpopular or controversial figures. David Segal, a writer for The Washington Post, calls the expression "the cliché of the 2008 campaign".
From Urban Dictionary:
One is thrown under the bus when they are made the scapegoat or blamed for something that wasn't their responsibility in the first place. A coverup for your mistake.
So this didn't happen in Lars' case, he wasn't blamed for the loss, wasn't made the scapegoat, didn't take the fall. Michel Therrien instead spoke of following the game plan and problems in the second period, nothing targeted at a specific player.