K3D can run at 100% CPU if out of memory. The lack of memory causes OOM for containers, which causes cascading failures which causes load on the server.
K3D is not configured with a memory cap at the moment, so this is constrained by your machine.
If a lot of services are frequently crashing, the K3D server will use a lot of resources to restart those
services until the CrashLoopBackOff
state is reached.