While undeniably there's great research out there that is and was funded by industry, including the food industry, there's really only one purpose for research like this - sales.
There's no doubt that if even the tiniest change had been found, the finding would have served industry as a talking and marketing point, just as was the case with the Welch's study that had them claiming grape juice gave working mothers better memories.
Those ends certainly aren't a mystery to the researchers who run these studies. And probably not a my$tery either as to why researchers agree to run them.
Maybe by way of a blind universal fund, or by way of sugar-sweetened beverage tax revenues, or by more innovative approaches (see below), we need to find new ways to fund research because clearly, research funding is broken, and it needs fixing.