The multiple choice format, which is unusual for a trivia show, helped proles follow along. If you give an open-ended prompt about the Battle of the Marne, the average viewer has no idea what you're on about and it's not fun for them-- hence why Jeopardy!, while popular, didn't have the same mass following. But if you give the viewers A/B/C/D, people can make a guess and still be playing at home, kinda. Plus the early questions are so easy that even proles can be happy they got SOMETHING right.

The 50/50 lifeline didn't do much, but the ask the audience or phone a friend were both good television-- again, do you trust the audience, will your friend actually know the answer, etc.

And the decision to walk away with current money or gamble added another fun element, and again people at home could argue about strategy or say what they would do.

Throw in a million dollar prize-- which at the time was a fair amount of money-- and you have some winning television. If they asked the exact same questions with a $500,000 prize but didn't have lifelines or multiple choice, then it would have been a dud.

(http://www.autoadmit.com/thread.php?thread_id=4811479&forum_id=2#42286380)