Not only was it made with Blender, the final renders were done with Blenders semi-realtime Eevee engine rather than its max-fidelity Cycles engine. That reduced the compute required by orders of magnitude - the director said a render farm wasn't necessary because his local workstation could produce final-quality 4K frames in 0.5-10 seconds. "Proper" production renderers like Cycles do look better of course, but havin…
Weren't Blender working on a more efficient cycles renderer?
It will never be on-par with Eevee's performance though as they are fundamentally different approaches to rendering: Cycles is a physically-based path-tracing engine, while Eevee uses rasterization through OpenGL.