Presumably ATC cleared him to land.
Sometimes an early decision to divert is a cop out. It can take skill and experience to get an aircraft safely and legally to destination in adverse conditions.
I don't know the details of this situation but it's quite possible he had committed to landing at Accra before the end of the runway became blocked.
I think you will find the flight landed legally and without knowing all the facts it would be wrong for anyone to infer the pilots acted irresponsibly.