This appeals to smart intelligent people who work during the week and therefore want to relax on the weekends, spend some time with the kids, and not be in a mob. Therefore, turn-out will be lower.
Glenn Beck's rally appealed to unemployed fat stupid idiots who had nothing better to do in 2010 than stand in the heat and listen to a radio shock jock cry and wet himself. Therefore, turn-out was higher.
Seriously, you want to hold a massive rally? Just hone your messaging to the dipshits of the world, and it never hurts to offer free pancakes or buttons or whatever the hell