Its the worst possible combination of a light aircraft and slippery runway, with plenty of residual thrust on those big motors.
I remember donkeys years ago in Newcastle, when a B727 positioning empty back to Manchester, slid off the contaminated taxiway. Red faces all around particularly when the same crew and aircraft repeated the entire scenario the following day, with exactly the same result. The airport director was pulling his hair out and jumping up and down, despite the fact that if they had cleared the rutted ice properly, it wouldn't have happened in the first place. The poor old training captain was dispatched to LGW for a spanking.