Why can’t this happen at Bayfront?

It's not that something like this can't happen at Bayfront, it's that no one with super deep pockets has tried it yet.

Would it be successful?

Well, it would be successful for the Dave Matthews Band and the people who want to see the Dave Matthews Band. The cost to the promoter to bring such an act in makes it a very dangerous endeavor, though.

Remember the annual 10,000 Lakes Festival in Detroit Lakes? That was going pretty good until they brought in the Dave Matthews Band. Now there is no more 10,000 Lakes Festival.

The reality is that there is great financial risk in putting together that kind of event. In the Twin Cities there is a huge population base to pull from. In Duluth, you have to pull in the same group of Twin Cities people to make it work. That requires a lot of expensive promotion.

Personally, I wouldn't even bet $100 that it will be sunny on a random day in July. But fortunately for all of us there are some folks who are bolder than I am. There's a pretty good selection of bands coming to Bayfront this summer, and if those shows do well the pickings will only improve.

First of all, Dave Matthews Band blows. Just because "lots of people like '90s-era jam-loving college-town rockers" doesn't make them suck any less.

Second, bands want a significant portion of their fee up front. So unless you have hundreds of thousands of dollars in liquid, cash money up front (don't forget your sound, garbage and security vendors!), and a venue that can accommodate 30,000+ fans, in an area that can reliably draw 30,000+ fans, the fancy bands (or rather, promoters like Live Nation, Clear Channel, AEG Live — even Sue McLean & Associates and Jam Productions) are just much less likely to come.

Does this make Bayfront "bad?" No. It is just not the Xcel Energy Center or Harriet Island or Somerset or Canterybury Park, with a proximal population base that numbers in the millions.

I erased that much-too-lengthy rant, so i'll provide some bullet points of my ideas/reaffirmations of Paul & Adam's:
-weather
-market base
-investors
-10pm sound ordinace (compliments city council,  poor geezer high rise placement)
-lack of Kosta's gyros for such a # of goers

The sum off those variables highlight why it's proabably a no go, at least immediately. But, I do say, keep what's currently going down there..I've had plenty of fun down there, seen great shows, and didn't have to line some greasy promoters pockets at the same time..

*didn't ridiculously line their pockets, at least..

Getting a sound extension until 11PM or 12AM isn't much of an issue. Vendors will come if you bring the crowd — the expansion of the Duluth-Superior Pride festival at Bayfront is a good example.