"They wanted something tangible and of value. Gold was a good fit because of its limited supply

[...] 

Fiat money has no value of its own and doesn’t represent anything of value, such as gold"

Usually this is where we laugh at fiat money for having no intrinsic value, but that misses the point that gold *also* has no intrinsic value. The only differences between fiat and gold are how easily more of it can be created, and more importantly, *who* can do that:

"The U.S. mines a lot of gold, but we’re not the biggest producer,” Wheelock said. “The bigger suppliers of gold would have more control over our monetary policy"

The purpose of fiat is not only to enable a cheap money spigot, but to be very specific about who controls it.