In Santa Clara, Calif., where the world’s biggest supplier of artificial-intelligence chips is based, Digital Realty Trust Inc. applied in 2019 to build a data center. Roughly six years later, the development remains an empty shell awaiting full energization. Stack Infrastructure, which was acquired earlier this year by Blue Owl Capital Inc., has a nearby 48-megawatt project that’s also vacant, while the city-owned utility, Silicon Valley Power, struggles to upgrade its capacity.