Don't get me wrong. I do think that pilots are able to safely land and taxi to the gate without the assistance of ATC, but: this shouldn't be allowed to happen and there ought to be procedures in place to prevent a controller from going offline due to fatigue or whatever.
But maybe it's the money which prevented two ATCOs to be present.
Remember the midair collision between a TU154 and a B757 overhead Überlingen / Germany in 2002? Resulting from a cut-down of personnel overhead proposed by a consulting firm, the Swiss controller was allowed to be alone at his station (his colleague was taking a scheduled break), handling a bunch of airplanes (several in upper airspace and one being vectored to an approach...) simultaneously and consequently overlooking the two airplanes on a conflicting course.