Can a kubernetes pod be forced to stay alive after its main command fails?
Keeping your pod alive after its main process exited is an anti-pattern and not possible in K8s.

The entire concept of a K8s Job is to run till completion. So what you are looking to do is neither ideal nor recommended.

It would be better to change the entrypoint command of your container to include a retry/error handling mechanism in case of failure.

With that said, you do have ways in which you can debug the failed pod.

If your Pod's container process exits due to error, the Pod will be marked with Status: Failed

But you can still debug the failed pod by attaching an Ephemeral container: https://kubernetes.io/docs/tasks/debug-application-cluster/debug-running-pod/#debugging-with-ephemeral-debug-container

Note: Ephemeral containers are available as K8s alpha feature only from v1.16