they thought lots of people were sitting at home, getting stoned, putting the tele on and turning down the sound, putting on some tunes and waiting for something bizarre to happen (no MTV remember). so hey, lets make a movie of world war two archive clips set to Beatles music.
So you were treated to the luftwaffe bombing the crap out of London while Leo ayer sang "I am the Walrus" with an orchestral backing.
Hats off to them, but I don't remember being impressed. And there were only about 3 other people in the cinema.