5G is a network technology that provides ultra-low latency, among other features. Latency measures the time it takes for a device to send a signal and get a response. And devices on a network with low latency can be more interactive.
Decentralized computing is when computing operations are performed across several devices connected via a network, rather than just on one device. Since these devices have to interact with each other, low latency is important to decentralized computing. And because 5G offers such low latency, it is an enabler of decentralized computing.