I also think it's the target demographic for the tourists that makes the difference. The Dells aims for young families with short attention spans.
Isn't the "legit" tourism season in Branson longer? (I have not been to Branson since I was about 14, so that's a long time ago.)
Back in the 80s, the Dells tried to do more Branson-type shows. The current Rick Wilcox theater was home to one of them. There was also "Fast Molly's", the Wisconsin Opry (still going, but hardly visible) and even the mis-step for live shows at Fort Dells -- if memory serves.
The Broadway Theater was a very nice venue that was doomed by opening for the first season very late and missing a lot of money. And frankly, the performances and food left a lot to be desired.
The Crystal Grand is a beautiful facility with great seating and sound that makes terrible booking choices -- IMHO. They are too pricey for locals and book acts that tourists can see twice a year in their home areas.
Ho-Chunk needs to buy Crystal Grand, so they have a venue for live acts. Seeing them at the casino is terrible. Bad seating, awful sightlines. 21 and over.