This flight (and its predecessors using a 763, which arrives from Europe and is probably a de-facto hot-spare for the European departures) has a long history of being delayed: it currently rates 0.0 out of 5 at FlightStats. This means that "this flight has on-time performance characteristics better than 0% of other flights", or is at the absolute bottom of the barrel nationwide. And it's not unusual to get a 757 substituted for the 763.

It shows out at 2047, so it looks they made it before the crew went illegal.