The KC Business Journal has an article for paid subscribers up on their website about the reason for the delays in the 3 Trails Project, including the Wizards soccer specific stadium. You can at least read a portion of the article and get an idea as to why. It would appear that the main reason for the delay is the fact that there is a disagreement between the developer and the state on the amount of square footage that would need to be developed to avoid a "clawback" provision.
The developer dropped the square footage they were willing to commit to when the "clawback" provision was brought up. This has caused the main delay in the $30 million in funds being released. Which has led to the construction delay at the site. For this to get approved, the developers and the state are going to have to reach an agreement. The way the economy is right now, though, it's going to be hard for the developers to get this going, especially with the problems with municipal bonds right now.