I think, before the lights were put in, Wrigley was a popular place for the yuppies at the Board of Trade or the Merc to go to play hookie. The "Bleacher Bum" craze was also popular, but I believe they only sold bleacher tickets on game days back then. Also, Wrigley is in a nicer neighborhood. All these things as well as the Tribune owning the Cubs, have added to their popularity over the years.
However, Cubs fans are still idiots who don't know s*** about baseball. I would never trade my years of misery to be a Cub fan. :fthecubs