To destroy an entire realm would destroy the balance of the other eight realms. Wiping out the people is a different matter.

If it were so simple to destroy another realm without repercussions for everyone else, do you truly think none of us would have tried it long before?

You may have your wish before long, since the damage is already done. Jötunheim is unstable now and without the Casket there is no real hope of repair.