The CEO of The Lego Group is obviously thrilled with their business, and what better way to express it than to bust out the theme song from their own movie? Like most serenades, it's hard to tell exactly how this went over. Usually when someone sings at you, it elicits a reaction of "please make it stop," so I think if you look at it from that perspective, it went pretty well!
He didn't even wait for applause! He just went straight his next order of business, also known as a shame spiral.