Well, that depends on the length of the runway and the types of aicraft involved!
I am not saying that is directly applies here; obviously the second aircraft was not warned by ATC by being given a "land after" clearance. I was merely pointing out that to say "You must never, ever, land on an occupied runway....period." is incorrect.
My view is that I do not have enough knowledge of the facts to form an opinion on whether it was a wise course of action, so I will leave it to the investigators who will go over it in fine detail to do so.