They were not serious about their sandboxing. Bugs in artifactory allowed escape, but they broke out of their Linux namespace/user by exploiting the kernel with an existing public cve. Sharing a kernel like that is not a serious barrier which is why cloud providers user virtualization for customer workloads.

Firecracker avoids sharing the whole kernel, and gvisor drastically reduces the attack surface of the kernel. Breaking through both layers would have been much more challenging and a demonstration of the model's capabilities rather than the sandbox's weakness.

Artifactory is self evidently not a security barrier, and as an exposed network service it should have been audited and after the first issues were found, rejected as a candidate. There's never just one security vulnerability.