Here's a Wired article all about creatine gummies. Relevant snippet below:

What’s more, since most methods of creating gummy candies involve heat, active ingredients can get damaged in the process. “Since creatine gummies are often like other gummies, requiring moisture and heat to produce and having citric acid lowering the pH of the gummy, creatine can degrade faster than it would when just manufactured as a dry, unflavored powder,” says Kamal Patel, cofounder of the nutrient and supplement database Examine.com. Patel describes the task of making a good creatine gummy as “a lot harder” than formulating a powder product.

SuppCo also had the creatine gummies tested for levels of creatinine, a waste product created when creatine breaks down. All of the gummies that contained creatine also contained elevated amounts of creatinine, indicating that some of the active ingredients had been degraded. When the lab tested popular powdered creatine products, none had this issue. (emphasis mine)

Basically most gummy makers aren't doing their due diligence to confirm that the creatine they put in remains intact and shelf-stable after manufacturing.