Nostalgia for the time they did it last year, basically.

I don't think there's any inherent bombast in Jerusalem with the normal tune. It all depends on the way it's done, and the way it's thought as well.

Land of Hope and Glory is pretty modern, tune's by Elgar, in the 1900s - he hated having it used for the song, which he thought was vulgar, not because he was particularly worried about imperialism and that.

Back in Thatcherism's darkest days I hated seeing it on the proms, because you could tell bastards meant it seriously and arrogantly. These days it comes across tongue in cheek, more akin to Gilbert and Sullivan:

"For he himself has said it
And it's greatly to his credit
That he is an Englishman, he is an Englishman..."